# Range extraction

Range extraction
You are encouraged to solve this task according to the task description, using any language you may know.

A format for expressing an ordered list of integers is to use a comma separated list of either

• individual integers
• Or a range of integers denoted by the starting integer separated from the end integer in the range by a dash, '-'. (The range includes all integers in the interval including both endpoints)
• The range syntax is to be used only for, and for every range that expands to more than two values.

Example
The list of integers:

-6, -3, -2, -1, 0, 1, 3, 4, 5, 7, 8, 9, 10, 11, 14, 15, 17, 18, 19, 20

Is accurately expressed by the range expression:

-6,-3-1,3-5,7-11,14,15,17-20

(And vice-versa).

• Create a function that takes a list of integers in increasing order and returns a correctly formatted string in the range format.
• Use the function to compute and print the range formatted version of the following ordered list of integers. (The correct answer is: `0-2,4,6-8,11,12,14-25,27-33,35-39`.)

```    0,  1,  2,  4,  6,  7,  8, 11, 12, 14,
15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
25, 27, 28, 29, 30, 31, 32, 33, 35, 36,
37, 38, 39
```
• Show the output of your program.

The provided solutions return an empty string, if the Sequence of integers is empty. Ranges with negative bounds are represented as -9--4, as the task requires. For real-life applications it is better to use the notation -9..-4.

### Iterative Solution

Since we don't know in advance how long the output will be, the iterative solution uses Unbounded_Strings.

procedure Range_Extraction is

```  type Sequence is array (Positive range <>) of Integer;
function Image (S : Sequence) return String is
Result : Unbounded_String;
From   : Integer;
procedure Flush (To : Integer) is
begin
if Length (Result) > 0 then
Append (Result, ',');
end if;
Append (Result, Trim (Integer'Image (From), Ada.Strings.Left));
if From < To then
if From+1 = To then
Append (Result, ',');
else
Append (Result, '-');
end if;
Append (Result, Trim (Integer'Image (To), Ada.Strings.Left));
end if;
end Flush;
begin
if S'Length > 0 then
From := S (S'First);
for I in S'First + 1..S'Last loop
if S (I - 1) + 1 /= S (I) then
Flush (S (I - 1));
From := S (I);
end if;
end loop;
Flush (S (S'Last));
end if;
end Image;
```

begin

```  Put_Line
(  Image
(  (  0,  1,  2,  4,  6,  7,  8, 11, 12, 14,
15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
25, 27, 28, 29, 30, 31, 32, 33, 35, 36,
37, 38, 39
)  )  );
```

end Range_Extraction;</lang>

### Recursive Solution

The recursive solution avoids the usage of unbounded strings.

procedure Range_Extract is

```  type Sequence is array (Positive range <>) of Integer;
```
```  function Img(I: Integer) return String is -- the image of an Integer
begin
return
end Img;
```
```  function Img(S: Sequence) return String is -- the image of a Sequence
```
```     function X(S : Sequence) return String is -- recursive eXtract
Idx: Positive := S'First;
begin
if S'Length = 0 then return
""; -- return nothing if Sequence is empty
else
while Idx < S'Last and then S(Idx+1) = S(Idx) + 1 loop
Idx := Idx + 1;
end loop;
if Idx = S'First then return
"," & Img(S(Idx)) & X(S(Idx+1 .. S'Last));
elsif Idx = S'First+1 then return
"," & Img(S(S'First)) & ',' & Img(S(Idx)) & X(S(Idx+1 .. S'Last));
else return
"," & Img(S(S'First)) & '-' & Img(S(Idx)) & X(S(Idx+1 .. S'Last));
end if;
end if;
end X;
```
```  begin -- function Img(S: Sequence) return String
if S'Length = 0 then return
"";
else return
Img(S(S'First)) & X(S(S'First+1 .. S'Last));
end if;
end Img;
```

begin -- main

```  Ada.Text_IO.Put_Line(Img( ( 0,  1,  2,  4,  6,  7,  8, 11, 12, 14, 15, 16,
17, 18, 19, 20, 21, 22, 23, 24, 25, 27, 28, 29,
30, 31, 32, 33, 35, 36, 37, 38, 39) ));
```

end Range_Extract;</lang>

Output:

The sample output is exactly the same, for both solutions:

`0-2,4,6-8,11,12,14-25,27-33,35-39`

## Aime

<lang aime>text rp(...) {

```   integer i, j;
data b;
text f;
```
```   i = 0;
j = 0;
while (i < count()) {
while (j < count() - 1) {
if (__integer(\$(j + 1)) == __integer(\$j) + 1) {
j += 1;
} else {
break;
}
}
if (i + 1 < j) {
b_form(b, "%s%d-%d", f, \$i, \$j);
f = ",";
} else {
while (i < j + 1) {
b_form(b, "%s%d", f, \$i);
f = ",";
i += 1;
}
}
```

j += 1; i = j;

```   }
```
```   return b_string(b);
```

}

integer main(void) {

```   o_form("%s\n", rp(0, 1, 2, 4, 6, 7, 8, 11, 12, 14, 15, 16, 17, 18, 19, 20,
21, 22, 23, 24, 25, 27, 28, 29, 30, 31, 32, 33, 35, 36,
37, 38, 39));
```
```   return 0;
```

}</lang>

Output:
`0-2,4,6-8,11,12,14-25,27-33,35-39`

## ALGOL 68

Note: The following Iterative code specimen is the "unrolled" version of the Generative code specimen below. Together they provided as a comparison of the two different methods.

### Iterative

Works with: ALGOL 68 version Revision 1 - one minor extension to language used - PRAGMA READ, similar to C's #include directive.
Works with: ALGOL 68G version Any - tested with release algol68g-2.3.2.
• The closest concept that Algol 68 has to duck typing is the tagged union. This is used to define mode urange = union(int, struct(int lwb, upb)). If duck typing was available it could reduced the size of the code specimen, but would have lost some of Algol 68's strong type data security.

File: Template_Range_extraction_Base.a68 <lang algol68>###

``` REQUIRES(MODE SCALAR, OP(SCALAR,SCALAR)BOOL =, OP(SCALAR,SCALAR)SCALAR +);
```

MODE SCALARLIST = FLEX[0]SCALAR; MODE YIELDINT = PROC(SCALAR)VOID;

1. Declarations for manipulating lists of range pairs [lwb:upb] #

MODE RANGE = STRUCT(SCALAR lwb, upb); MODE RANGELIST = FLEX[0]RANGE; MODE YIELDRANGE = PROC(RANGE)VOID;

PROC range repr = (RANGE range)STRING: (

``` STRING lwb := whole(lwb OF range,0);
IF lwb OF range = upb OF range THEN
lwb
ELSE
# "["+lwb+":"+whole(upb OF range,0)+"]"  #
lwb+"-"+whole(upb OF range,0)
FI
```

);

1. OP REPR = (RANGE range)STRING: range repr(range); # # firmly related to UNIRANGE #
1. Declarations for manipulating lists containing pairs AND lone INTs #

MODE UNIRANGE = UNION(SCALAR, RANGE); MODE UNIRANGELIST = FLEX[0]UNIRANGE; MODE YIELDUNIRANGE = PROC(UNIRANGE)VOID;

PROC unirange repr = (UNIRANGE unirange)STRING:

``` CASE unirange IN
(RANGE range): range repr(range),
(SCALAR scalar): whole(scalar,0)
ESAC;
```

OP (UNIRANGE)STRING REPR = unirange repr; # alias #

1. The closest thing Algol68 has to inheritance is the UNION #

MODE UNIRANGELISTS = UNION(UNIRANGELIST, RANGELIST, SCALARLIST);

PROC unirange list repr = (UNIRANGELIST unirange list)STRING: (

1. Produce a STRING representation of a UNIRANGELIST ###
``` STRING out # := "("#, sep := "";
FOR key FROM LWB unirange list TO UPB unirange list DO
out +:= sep + REPR unirange list[key];
sep := "," # +" " #
OD;
out # +")" #
```

);

OP (UNIRANGELIST)STRING REPR = unirange list repr; # alias #</lang>File: Template_Range_extraction_Iterative.a68 <lang algol68>###

``` REQUIRES(MODE SCALAR, OP(SCALAR,SCALAR)BOOL =, OP(SCALAR,SCALAR)SCALAR +);
```

OP (UNIRANGELISTS)UNIRANGELIST INITUNIRANGE = init unirange list; # alias #

PROC init unirange list = (UNIRANGELISTS unirange list)UNIRANGELIST: (

1. Take a []SCALAR, []RANGE or []UNIRANGE, and return a normalised []UNIRANGE ###
``` INT len = UPB unirange list-LWB unirange list+1;
[LWB unirange list: LWB unirange list+len*2]UNIRANGE out unirange list;
SCALAR upb out unirange list := LWB out unirange list - 1;
UNION(VOID, RANGE) prev range := EMPTY;
```
``` PROC out unirange list append = (RANGE value)VOID:(
```
```   IF lwb OF value = upb OF value THEN
out unirange list[upb out unirange list+:=1] := lwb OF value
ELIF lwb OF value + 1 = upb OF value THEN
out unirange list[upb out unirange list+:=1] := lwb OF value;
out unirange list[upb out unirange list+:=1] := upb OF value
ELSE
out unirange list[upb out unirange list+:=1] := value
FI
);
```
``` FOR key FROM LWB unirange list TO UPB unirange list DO
UNIRANGE value = CASE unirange list IN
(SCALARLIST list):list[key],
(RANGELIST list):list[key],
(UNIRANGELIST list):list[key]
ESAC;
```
```   RANGE next range := CASE value IN
(RANGE range): range,
(SCALAR value): RANGE(value, value)
ESAC;
```
```   prev range :=
CASE prev range IN
(VOID): next range,
(RANGE prev range):
IF upb OF prev range + 1 = lwb OF next range THEN
RANGE(lwb OF prev range, upb OF next range) # merge the range #
ELSE
out unirange list append(prev range);
next range
FI
OUT SKIP
ESAC
```
``` OD;
```
``` CASE prev range IN
(RANGE last range): out unirange list append(last range)
ESAC;
```
``` out unirange list[:upb out unirange list]
```

);</lang>File: test_Range_extraction_Integer.a68<lang algol68>#!/usr/local/bin/a68g --script #

1. some simple test cases: #

MODE SCALAR = INT; PR READ "Template_Range_extraction_Iterative.a68" PR

MODE RANGEINT = UNIRANGE;

test: BEGIN

``` []INT int list = ( # unnormalised #
0,  1,  2,  4,  6,  7,  8, 11, 12, 14,
15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
25, 27, 28, 29, 30, 31, 32, 33, 35, 36,
37, 38, 39);
```
``` []RANGE range list = ( # unnormalised #
(0,0),  (1,1),  (2,2),  (4,4),  (6,6),  (7,7),  (8,8), (11,11), (12,12), (14,14),
(15,15), (16,16), (17,17), (18,18), (19,19), (20,20), (21,21), (22,22), (23,23), (24,24),
(25,25), (27,27), (28,28), (29,29), (30,30), (31,31), (32,32), (33,33), (35,35), (36,36),
(37,37), (38,38), (39,39));
```
``` []RANGEINT list a = ( # unnormalised #
RANGE(0,2), 4, RANGE(6,8), RANGE(11,12),
RANGE(14,25), RANGE(27,33), RANGE(35,39));
```
``` []RANGEINT list b = ( # unnormalised #
0,  1,  2,  4,  6,  7,  8, 11, 12, 14,
15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
25, 27, 28, 29, 30, 31, 32, 33, 35, 36,
37, 38, 39);
```
``` []RANGEINT list c = INITUNIRANGE(list b); # normalised #
```
1. compare manipulation of various types of argument lists #
``` printf((\$gl\$,
REPR INITUNIRANGE int list,
REPR INITUNIRANGE range list,
REPR INITUNIRANGE list a,
REPR INITUNIRANGE list b,
REPR list c
))
```

END</lang>

Output:
```0-2,4,6-8,11,12,14-25,27-33,35-39
0-2,4,6-8,11,12,14-25,27-33,35-39
0-2,4,6-8,11,12,14-25,27-33,35-39
0-2,4,6-8,11,12,14-25,27-33,35-39
0-2,4,6-8,11,12,14-25,27-33,35-39
```

### Generative

Works with: ALGOL 68 version Revision 1 - one minor extension to language used - PRAGMA READ, similar to C's #include directive.
Works with: ALGOL 68G version Any - tested with release algol68g-2.3.2.
• The following code a set of helper functions/generators that can be used to manipulate a lists of ranges. They can manipulate either arrays or iterator. And they can handle data of type int or range and both these types unioned.

These chained iterators do the following steps:

1. Iterate through three different types of initial arrays - []int, []range and []unirange with gen range, yielding range(lwb,upb)
2. Iterate with gen range merge yielding merged range(lwb,upb)
3. Iterate with gen unirange merge, merging and yielding a union of int and range
4. Finally iterate with unirange list init exiting with an array of union of int and range.

File: Template_Range_extraction_Generative.a68 <lang algol68>###

``` REQUIRES(MODE SCALAR, OP(SCALAR,SCALAR)BOOL =, OP(SCALAR,SCALAR)SCALAR +);
```

PROC gen range = (UNIRANGELISTS unirange list, YIELDRANGE yield range)VOID:

1. Take a []SCALAR, []RANGE or []URANGE, and generatively yield an unnormalised RANGE ###
``` FOR key FROM LWB unirange list TO UPB unirange list DO
```
1. Note: Algol 68RS cannot handle LWB and UPB of a UNION in the following: #
```   UNIRANGE value = CASE unirange list IN
(SCALARLIST list):list[key],
(RANGELIST list):list[key],
(UNIRANGELIST list):list[key]
ESAC;
yield range(
CASE value IN
(RANGE range): range,
(SCALAR value): (value, value)
ESAC
)
OD;
```

PROC gen range merge = (UNIRANGELISTS unirange list, YIELDRANGE yield)VOID: (

1. Take a []SCALAR, []RANGE or []URANGE , and generatively yield a normalised RANGE ###
``` UNION(VOID, RANGE) prev range := EMPTY;
```
1. FOR RANGE next range IN # gen range(unirange list, # ) DO #
1. (RANGE next range)VOID:
2. if the ranges cannot be merge, then yield 1st, and return 2nd #
```   prev range :=
CASE prev range IN
(VOID): next range,
(RANGE prev range):
IF upb OF prev range + 1 = lwb OF next range THEN
RANGE(lwb OF prev range, upb OF next range) # merge the range #
ELSE
#IF lwb OF prev range <= upb OF prev range THEN#
yield(prev range);
#FI;#
next range
FI
OUT SKIP
ESAC
```
1. OD # );
``` CASE prev range IN (RANGE last range): yield(last range) ESAC
```

);

PROC gen unirange merge = (UNIRANGELISTS unirange list, YIELDUNIRANGE yield)VOID: (

1. Take a []SCALAR, []RANGE or []UNIRANGE and generatively yield a normalised UNIRANGE ###
``` PROC unpack = (RANGE value)VOID:(
IF lwb OF value = upb OF value THEN
yield(lwb OF value)
ELIF lwb OF value + 1 = upb OF value THEN
yield(lwb OF value);
yield(upb OF value)
ELSE
yield(value)
FI
);
```
``` gen range merge(unirange list, unpack)
```

);

PROC unirange list init = (UNIRANGELISTS unirange list)UNIRANGELIST: (

1. Take a []SCALAR, []RANGE or []UNIRANGE and return a static []UNIRANGE ###
``` INT len = UPB unirange list - LWB unirange list + 1;
[LWB unirange list: LWB unirange list + len * 2]UNIRANGE out unirange list; # estimate #
SCALAR upb out unirange list := LWB out unirange list - 1;
```
1. FOR UNIRANGE unirange IN # gen unirange merge(unirange list, # ) DO #
1. (UNIRANGE unirange)VOID:
```   out unirange list[upb out unirange list+:=1] := unirange
```
1. OD # );
``` out unirange list[:upb out unirange list]
```

);

OP (UNIRANGELISTS)UNIRANGELIST INITUNIRANGE = unirange list init; # alias #</lang>

Output:
```0-2,4,6-8,11,12,14-25,27-33,35-39
0-2,4,6-8,11,12,14-25,27-33,35-39
0-2,4,6-8,11,12,14-25,27-33,35-39
0-2,4,6-8,11,12,14-25,27-33,35-39
0-2,4,6-8,11,12,14-25,27-33,35-39
```

## AppleScript

Translation of: JavaScript

<lang AppleScript>-- rangeFormat :: [Int] -> String on rangeFormat(xs)

```   script nonConsec
on lambda(a, b)
b - a > 1
end lambda
end script

intercalate(",", map(my rangeString, splitBy(nonConsec, xs)))
```

end rangeFormat

-- rangeString :: [Int] -> String on rangeString(xs)

```   if length of xs > 2 then
(item 1 of xs as string) & "-" & (item -1 of xs as string)
else
intercalate(",", xs)
end if
```

end rangeString

--TEST on run

```   set xs to {0, 1, 2, 4, 6, 7, 8, 11, 12, 14, 15, 16, ¬
17, 18, 19, 20, 21, 22, 23, 24, 25, 27, 28, 29, 30, 31, 32, ¬
33, 35, 36, 37, 38, 39}

rangeFormat(xs)

--> "0-2,4,6-8,11,12,14-25,27-33,35-39"
```

end run

-- GENERIC FUNCTIONS

-- splitBy :: (a -> a -> Bool) -> [a] -> a on splitBy(f, xs)

```   set mf to mReturn(f)

if length of xs < 2 then
{xs}
else
script p
on lambda(a, x)
set {acc, active, prev} to a
if mf's lambda(prev, x) then
{acc & {active}, {x}, x}
else
{acc, active & x, x}
end if
end lambda
end script

set h to item 1 of xs
set lstParts to foldl(p, {{}, {h}, h}, items 2 thru -1 of xs)
item 1 of lstParts & {item 2 of lstParts}
end if
```

end splitBy

-- foldl :: (a -> b -> a) -> a -> [b] -> a on foldl(f, startValue, xs)

```   tell mReturn(f)
set v to startValue
set lng to length of xs
repeat with i from 1 to lng
set v to lambda(v, item i of xs, i, xs)
end repeat
return v
end tell
```

end foldl

-- map :: (a -> b) -> [a] -> [b] on map(f, xs)

```   tell mReturn(f)
set lng to length of xs
set lst to {}
repeat with i from 1 to lng
set end of lst to lambda(item i of xs, i, xs)
end repeat
return lst
end tell
```

end map

-- intercalate :: Text -> [Text] -> Text on intercalate(strText, lstText)

```   set {dlm, my text item delimiters} to {my text item delimiters, strText}
set strJoined to lstText as text
set my text item delimiters to dlm
return strJoined
```

end intercalate

-- Lift 2nd class handler function into 1st class script wrapper -- mReturn :: Handler -> Script on mReturn(f)

```   if class of f is script then
f
else
script
property lambda : f
end script
end if
```

end mReturn</lang>

Output:
`0-2,4,6-8,11,12,14-25,27-33,35-39`

## AutoHotkey

<lang AutoHotkey>msgbox % extract("0,1,2,4,6,7,8,11,12,14,15,16,17,18,19,20,21,22,23,24,25,27,28,29,30,31,32,33,35,36,37,38,39")

extract( list ) {

```   loop, parse, list, `,, %A_Tab%%A_Space%`r`n
{
if (A_LoopField+0 != p+1)
ret .= (f!=p ? (p>f+1 ? "-" : ",") p : "") "," f := A_LoopField
p := A_LoopField
}
return SubStr(ret (f!=p ? (p>f+1 ? "-" : ",") p : ""), 2)
```

}</lang>

Output:
```---------------------------
Range extraction.ahk
---------------------------
0-2,4,6-8,11,12,14-25,27-33,35-39
---------------------------
OK
---------------------------```

## AWK

AWK is a primitive bird that prefers global scope for arrays.

Local variables for functions are declared in the parameters and, by convention, separated from the expected ones by extra space.

<lang awk>#!/usr/bin/awk -f

BEGIN {

```   delete sequence
delete range
```
```   seqStr = "0,1,2,4,6,7,8,11,12,14,15,16,17,18,19,20,21,22,23,24,"
seqStr = seqStr "25,27,28,29,30,31,32,33,35,36,37,38,39"
print "Sequence: " seqStr
fillSequence(seqStr)
rangeExtract()
showRange()
exit
```

}

function rangeExtract( runStart, runLen) {

```   delete range
runStart = 1
while(runStart <= length(sequence)) {
runLen = getSeqRunLen(runStart)
runStart += runLen
}
```

}

function getSeqRunLen(startPos, pos) {

```   for (pos = startPos; pos < length(sequence); pos++) {
if (sequence[pos] + 1 != sequence[pos + 1]) break;
}
return pos - startPos + 1;
```

}

```   if (len == 1) str = sequence[startPos]
else if (len == 2) str = sequence[startPos] "," sequence[startPos + 1]
else str = sequence[startPos] "-" sequence[startPos + len - 1]
range[length(range) + 1] = str
```

}

function showRange( r) {

```   printf "  Ranges: "
for (r = 1; r <= length(range); r++) {
if (r > 1) printf ","
printf range[r]
}
printf "\n"
```

}

function fillSequence(seqStr, n, s) {

```   n = split(seqStr,a,/[,]+/)
for (s = 1; s <= n; s++) {
sequence[s] = a[s]
}
```

}</lang>

Output:
``` Sequence: 0,1,2,4,6,7,8,11,12,14,15,16,17,18,19,20,21,22,23,24,25,27,28,29,30,31,32,33,35,36,37,38,39
Ranges: 0-2,4,6-8,11,12,14-25,27-33,35-39
```

## BBC BASIC

<lang bbcbasic> range\$ = " 0, 1, 2, 4, 6, 7, 8, 11, 12, 14, " + \

```     \        "15, 16, 17, 18, 19, 20, 21, 22, 23, 24, " + \
\        "25, 27, 28, 29, 30, 31, 32, 33, 35, 36, " + \
\        "37, 38, 39"
PRINT FNrangeextract(range\$)
END

DEF FNrangeextract(r\$)
LOCAL f%, i%, r%, t%, t\$
f% = VAL(r\$)
REPEAT
i% = INSTR(r\$, ",", i%+1)
t% = VALMID\$(r\$, i%+1)
IF t% = f% + r% + 1 THEN
r% += 1
ELSE
CASE r% OF
WHEN 0: t\$ += STR\$(f%) + ","
WHEN 1: t\$ += STR\$(f%) + "," + STR\$(f% + r%) + ","
OTHERWISE: t\$ += STR\$(f%) + "-" + STR\$(f% + r%) + ","
ENDCASE
r% = 0
f% = t%
ENDIF
UNTIL i% = 0
= LEFT\$(t\$)</lang>
```
Output:
```0-2,4,6-8,11,12,14-25,27-33,35-39
```

## Bracmat

<lang bracmat> ( rangeExtract

``` =     accumulator firstInRange nextInRange
, accumulate fasten rangePattern
.   ( accumulate
=     !accumulator
(!accumulator:|?&",")
!firstInRange
(   !firstInRange+1:<>!nextInRange
&   ( !firstInRange+2:!nextInRange&","
| "-"
)
-1+!nextInRange
|
)
: ?accumulator
)
& ( fasten
= [%( !accumulate
& (!sjt:?firstInRange)+1:?nextInRange
)
)
& ( rangePattern
=   (
|   ?
( !nextInRange
& 1+!nextInRange:?nextInRange
)
)
( &!accumulate
| (#<>!nextInRange:!fasten) !rangePattern
)
)
& :?accumulator:?firstInRange
& !arg:(|#!fasten !rangePattern)
& str\$!accumulator
)
```

& ( test

``` =   L A
.   put\$(!arg " ==>\n",LIN)
& (   !arg:(?,?)
& whl'(!arg:(?A,?arg)&(!A,!L):?L)
& whl'(!L:(?A,?L)&!A !arg:?arg)
|
)
& out\$(rangeExtract\$!arg)
)
```

& test

``` \$ (0,  1,  2,  4,  6,  7,  8, 11, 12, 14,
15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
25, 27, 28, 29, 30, 31, 32, 33, 35, 36,
37, 38, 39)</lang>
```
Output:
```(0,1,2,4,6,7,8,11,12,14,15,16,17,18,19,20,21,22,23,24,25,27,28,29,30,31,32,33,35,36,37,38,39)  ==>
0-2,4,6-8,11,12,14-25,27-33,35-39```

## C

Using the fine tradition of `snprintf`, `rprint` is not responsible for allocating output buffer. It prints the range only if supplied a non-null pointer, but always returns the output length sans the terminating null, so caller can allocate buffer. <lang c>#include <stdio.h>

1. include <stdlib.h>

size_t rprint(char *s, int *x, int len) {

1. define sep (a > s ? "," : "") /* use comma except before first output */
2. define ol (s ? 100 : 0) /* print only if not testing for length */

int i, j; char *a = s; for (i = j = 0; i < len; i = ++j) { for (; j < len - 1 && x[j + 1] == x[j] + 1; j++);

if (i + 1 < j) a += snprintf(s?a:s, ol, "%s%d-%d", sep, x[i], x[j]); else while (i <= j) a += snprintf(s?a:s, ol, "%s%d", sep, x[i++]); } return a - s;

1. undef sep
2. undef ol

}

int main() { int x[] = { 0, 1, 2, 4, 6, 7, 8, 11, 12, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 27, 28, 29, 30, 31, 32, 33, 35, 36, 37, 38, 39 };

char *s = malloc(rprint(0, x, sizeof(x) / sizeof(int)) + 1); rprint(s, x, sizeof(x) / sizeof(int)); printf("%s\n", s);

return 0; }</lang>

Output:
`0-2,4,6-8,11,12,14-25,27-33,35-39`

## C++

<lang cpp>

1. include <iostream>
2. include <iterator>
3. include <cstddef>

template<typename InIter>

```void extract_ranges(InIter begin, InIter end, std::ostream& os)
```

{

``` if (begin == end)
return;
```
``` int current = *begin++;
os << current;
int count = 1;
```
``` while (begin != end)
{
int next = *begin++;
if (next == current+1)
++count;
else
{
if (count > 2)
os << '-';
else
os << ',';
if (count > 1)
os << current << ',';
os << next;
count = 1;
}
current = next;
}
```
``` if (count > 1)
os << (count > 2? '-' : ',') << current;
```

}

template<typename T, std::size_t n>

```T* end(T (&array)[n])
```

{

``` return array+n;
```

}

int main() {

``` int data[] = { 0,  1,  2,  4,  6,  7,  8, 11, 12, 14,
15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
25, 27, 28, 29, 30, 31, 32, 33, 35, 36,
37, 38, 39 };
```
``` extract_ranges(data, end(data), std::cout);
std::cout << std::endl;
```

} </lang>

Output:
``` 0-2,4,6-8,11,12,14-25,27-33,35-39
```

## C#

<lang csharp>using System; using System.Collections.Generic; using System.Linq;

class RangeExtraction {

```   static void Main()
{
const string testString = "0,  1,  2,  4,  6,  7,  8, 11, 12, 14,15, 16, 17, 18, 19, 20, 21, 22, 23, 24,25, 27, 28, 29, 30, 31, 32, 33, 35, 36,37, 38, 39";
var result = String.Join(",", RangesToStrings(GetRanges(testString)));
Console.Out.WriteLine(result);
}
```
```   public static IEnumerable<IEnumerable<int>> GetRanges(string testString)
{
var numbers = testString.Split(new[] { ',' }).Select(x => Convert.ToInt32(x));
var current = new List<int>();
foreach (var n in numbers)
{
if (current.Count == 0)
{
}
else
{
if (current.Max() + 1 == n)
{
}
else
{
yield return current;
current = new List<int> { n };
}
}
}
yield return current;
}
```
```   public static IEnumerable<string> RangesToStrings(IEnumerable<IEnumerable<int>> ranges)
{
foreach (var range in ranges)
{
if (range.Count() == 1)
{
yield return range.Single().ToString();
}
else if (range.Count() == 2)
{
yield return range.Min() + "," + range.Max();
}
else
{
yield return range.Min() + "-" + range.Max();
}
}
}
```

} </lang>

Output:
`0-2,4,6-8,11,12,14-25,27-33,35-39`

### C#: Alternate Version

 This example is incorrect. Please fix the code and remove this message.Details: 11-12 is wrong. Check the spec.

<lang csharp>using System; using System.Collections.Generic; using System.Linq;

namespace RangeExtraction {

``` internal static class ListExtensions {
internal static string ExtractRange(this IEnumerable<int> values) {
var list = values.Distinct().OrderBy(_ => _).ToArray();
var ranges = new int[0][].AsEnumerable();
var current = 0;
for (var i = 1; ; ++i) {
if (i >= list.Length) {
ranges = ranges.Concat(new[] { new[] { i != current ? current : i - 1, i - 1 } });
break;
}
if (list[i] == list[i - 1] + 1)
continue;
ranges = ranges.Concat(new[] { new[] { current, i - 1 } });
current = i;
}
return string.Join(",", ranges.Select(r => string.Format(r[0] == r[1] ? "{0}" : "{0}-{1}", list[r[0]], list[r[1]])));
}
}
```
``` internal class Program {
private static readonly IList<int> VALUES = new[] {
0, 1, 2,
4,
6, 7, 8,
11, 12,
14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25,
27, 28, 29, 30, 31, 32, 33,
35, 36, 37, 38, 39
};
```
```   private static void Main(string[] args) {
var rangestr = VALUES.ExtractRange();
Console.WriteLine("values: {{{0}}}", string.Join(", ", VALUES.Select(_=>_.ToString())));
Console.WriteLine("\r\nranges = \"{0}\"", rangestr);
}
}
```

}</lang>

Output:
```values: {0, 1, 2, 4, 6, 7, 8, 11, 12, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 27, 28, 29, 30, 31, 32, 33, 35, 36, 37, 38, 39}
ranges = "0-2,4,6-8,11-12,14-25,27-33,35-39"```

## Ceylon

<lang ceylon>shared void run() {

value numbers = [ 0, 1, 2, 4, 6, 7, 8, 11, 12, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 27, 28, 29, 30, 31, 32, 33, 35, 36, 37, 38, 39 ];

function asRangeFormattedString<Value>([Value*] values) given Value satisfies Enumerable<Value> {

value builder = StringBuilder();

void append(Range<Value> range) { if(!builder.empty) { builder.append(","); } if(1 <= range.size < 3) { builder.append(",".join(range)); } else { builder.append("``range.first``-``range.last``"); } }

if(nonempty values) { variable value currentRange = values.first..values.first; for(val in values.rest) { if(currentRange.last.successor == val) { currentRange = currentRange.first..val; } else { append(currentRange); currentRange = val..val; } } append(currentRange); } return builder.string; }

value rangeString = asRangeFormattedString(numbers); assert(rangeString == "0-2,4,6-8,11,12,14-25,27-33,35-39"); print(rangeString); }</lang>

Output:
`0-2,4,6-8,11,12,14-25,27-33,35-39`

## COBOL

Works with: OpenCOBOL

<lang cobol> IDENTIFICATION DIVISION.

```      PROGRAM-ID. extract-range-task.

DATA DIVISION.
WORKING-STORAGE SECTION.
01  data-str                PIC X(200) VALUE "0,  1,  2,  4,  6,"
& " 7,  8, 11, 12, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, "
& "24, 25, 27, 28, 29, 30, 31, 32, 33, 35, 36, 37, 38, 39".

01  result                  PIC X(200).

PROCEDURE DIVISION.
CALL "extract-range" USING CONTENT data-str, REFERENCE result
DISPLAY FUNCTION TRIM(result)

GOBACK
.

IDENTIFICATION DIVISION.
PROGRAM-ID. extract-range.

DATA DIVISION.
LOCAL-STORAGE SECTION.
COPY "nums-table.cpy".

01  difference              PIC 999.

01  rng-begin               PIC S999.
01  rng-end                 PIC S999.

01  num-trailing            PIC 999.

01  trailing-comma-pos      PIC 999.
```
```      LINKAGE SECTION.
01  nums-str                PIC X(200).
01  extracted-range         PIC X(200).

01  extracted-range-len     CONSTANT LENGTH extracted-range.
```
```      PROCEDURE DIVISION USING nums-str, extracted-range.
CALL "split-nums" USING CONTENT nums-str, ", ",
REFERENCE nums-table

*> Process the table
MOVE nums (1) TO rng-begin
PERFORM VARYING nums-idx FROM 2 BY 1
UNTIL num-nums < nums-idx
SUBTRACT nums (nums-idx - 1) FROM nums (nums-idx)
GIVING difference

*> If number is more than one away from the previous one
*> end the range and start a new one.
IF difference > 1
MOVE nums (nums-idx - 1) TO rng-end
rng-end, REFERENCE extracted-range
MOVE nums (nums-idx) TO rng-begin
END-IF
END-PERFORM

*> Process the last number
MOVE nums (num-nums) TO rng-end
rng-end, REFERENCE extracted-range

*> Remove trailing comma.
CALL "find-num-trailing-spaces"
USING CONTENT extracted-range, REFERENCE num-trailing
COMPUTE trailing-comma-pos =
extracted-range-len - num-trailing
MOVE SPACE TO extracted-range (trailing-comma-pos:1)

GOBACK
.

IDENTIFICATION DIVISION.
PROGRAM-ID. split-nums INITIAL.

DATA DIVISION.
WORKING-STORAGE SECTION.
01  num-len                 PIC 9.
01  next-num-pos            PIC 999.

01  str                     PIC X(200).
01  delim                   PIC X ANY LENGTH.

COPY "nums-table.cpy".

PROCEDURE DIVISION USING str, delim, nums-table.
INITIALIZE num-nums

PERFORM UNTIL str = SPACES
INITIALIZE num-len
INSPECT str TALLYING num-len FOR CHARACTERS BEFORE delim

*> If there are no more instances of delim in the string,
*> add the rest of the string to the last element of the
*> table.
IF num-len = 0
MOVE str TO nums (num-nums)
EXIT PERFORM
ELSE
MOVE str (1:num-len) TO nums (num-nums)
ADD 3 TO num-len GIVING next-num-pos
MOVE str (next-num-pos:) TO str
END-IF
END-PERFORM
.
END PROGRAM split-nums.

IDENTIFICATION DIVISION.
```
```      DATA DIVISION.
WORKING-STORAGE SECTION.
01  num-trailing            PIC 999.
01  start-pos               PIC 999.

01  range-len               PIC 999.

01  begin-edited            PIC -ZZ9.
01  end-edited              PIC -ZZ9.
```
```      LINKAGE SECTION.
01  rng-begin               PIC S999.
01  rng-end                 PIC S999.

01  extracted-range         PIC X(200).
```
```      01  extracted-range-len     CONSTANT LENGTH extracted-range.

PROCEDURE DIVISION USING rng-begin, rng-end, extracted-range.
CALL "find-num-trailing-spaces"
USING CONTENT extracted-range, REFERENCE num-trailing
COMPUTE start-pos = extracted-range-len - num-trailing + 1

SUBTRACT rng-begin FROM rng-end GIVING range-len

MOVE rng-begin TO begin-edited
MOVE rng-end TO end-edited
```
```          EVALUATE TRUE
WHEN rng-begin = rng-end
STRING FUNCTION TRIM(begin-edited), ","
INTO extracted-range (start-pos:)

WHEN range-len = 1
STRING FUNCTION TRIM(begin-edited), ",",
FUNCTION TRIM(end-edited), ","
INTO extracted-range (start-pos:)

WHEN OTHER
STRING FUNCTION TRIM(begin-edited), "-",
FUNCTION TRIM(end-edited), ","
INTO extracted-range (start-pos:)
END-EVALUATE
.

IDENTIFICATION DIVISION.
PROGRAM-ID. find-num-trailing-spaces.

DATA DIVISION.
01  str                     PIC X(200).
01  num-trailing            PIC 999.

PROCEDURE DIVISION USING str, num-trailing.
INITIALIZE num-trailing
INSPECT str TALLYING num-trailing FOR TRAILING SPACES
.
END PROGRAM find-num-trailing-spaces.

END PROGRAM extract-range.</lang>
```

nums-table.cpy: <lang cobol> 01 nums-table.

```          03  num-nums            PIC 999.
03  nums-area.
05  nums            PIC S999 OCCURS 1 TO 100 TIMES
DEPENDING ON num-nums
INDEXED BY nums-idx.</lang>
```
Output:
```0-2,4,6-8,11,12,14-25,27-33,35-39
```

## Common Lisp

<lang lisp>(defun format-with-ranges (list)

``` (unless list (return ""))
(with-output-to-string (s)
(let ((current (first list))
(list    (rest list))
(count   1))
(princ current s)
(dolist (next list)
(if (= next (1+ current))
(incf count)
(progn (princ (if (> count 2) "-" ",") s)
(when (> count 1)
(princ current s)
(princ "," s))
(princ next s)
(setf count 1)))
(setf current next))
(when (> count 1)
(princ (if (> count 2) "-" ",") s)
(princ current s)))))
```

CL-USER> (format-with-ranges (list 0 1 2 4 6 7 8 11 12 14

```                                  15 16 17 18 19 20 21 22 23 24
25 27 28 29 30 31 32 33 35 36
37 38 39))
```

"0-2,4,6-8,11,12,14-25,27-33,35-39" </lang>

## D

<lang d>import std.stdio, std.conv, std.string, std.algorithm, std.range;

string rangeExtraction(in int[] items) in {

```   assert(items.isSorted);
```

} body {

```   if (items.empty)
return null;
auto ranges = [[items[0].text]];
```
```   foreach (immutable x, immutable y; items.zip(items[1 .. \$]))
if (x + 1 == y)
ranges[\$ - 1] ~= y.text;
else
ranges ~= [y.text];
```
```   return ranges
.map!(r => r.length > 2 ? r[0] ~ "-" ~ r.back : r.join(','))
.join(',');
```

}

void main() {

```   foreach (data; [[-8, -7, -6, -3, -2, -1, 0, 1, 3, 4, 5, 7, 8, 9,
10, 11, 14, 15, 17, 18, 19, 20],
[0, 0, 0, 1, 1],
[0, 1, 2, 4, 6, 7, 8, 11, 12, 14, 15, 16, 17, 18,
19, 20, 21, 22, 23, 24, 25, 27, 28, 29, 30, 31,
32, 33, 35, 36, 37, 38, 39]])
data.rangeExtraction.writeln;
```

}</lang>

Output:
```-8--6,-3-1,3-5,7-11,14,15,17-20
0,0,0,1,1
0-2,4,6-8,11,12,14-25,27-33,35-39```

## DWScript

<lang delphi>procedure ExtractRanges(const values : array of Integer); begin

```  var i:=0;
while i<values.Length do begin
if i>0 then
Print(',');
Print(values[i]);
var j:=i+1;
while (j<values.Length) and (values[j]=values[j-1]+1) do
Inc(j);
Dec(j);
if j>i then begin
if j=i+1 then
Print(',')
else Print('-');
Print(values[j]);
end;
i:=j+1;
end;
```

end;

ExtractRanges([ 0, 1, 2, 4, 6, 7, 8, 11, 12, 14,

```              15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
25, 27, 28, 29, 30, 31, 32, 33, 35, 36,
37, 38, 39]);</lang>
```
Output:
`0-2,4,6-8,11,12,14-25,27-33,35-39`

## E

Cheeky solution: relying on the standard library for finding ranges, and just formatting them ourselves.

<lang e>def rex(numbers :List[int]) {

```   var region := 0..!0
for n in numbers { region |= n..n }
var ranges := []
for interval in region.getSimpleRegions() {
def a := interval.getOptStart()
def b := interval.getOptBound() - 1
ranges with= if (b > a + 1) {
`\$a-\$b`
} else if (b <=> a + 1) {
`\$a,\$b`
} else { # b <=> a
`\$a`
}
}
return ",".rjoin(ranges)
```

}</lang>

<lang e>? rex([ > 0, 1, 2, 4, 6, 7, 8, 11, 12, 14, > 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, > 25, 27, 28, 29, 30, 31, 32, 33, 35, 36, > 37, 38, 39])

1. value: "0-2,4,6-8,11,12,14-25,27-33,35-39"

</lang>

## EchoLisp

<lang scheme> (define task '(0 1 2 4 6 7 8 11 12 14 15 16 17 18 19 20 21 22 23 24 25 27 28 29 30 31 32 33 35 36 37 38 39))

1- GROUPING

(define (group-range item acc) (if

```   (or (empty? acc) (!= (caar acc) (1- item)))
(cons (cons item item) acc)
(begin  (set-car! (car acc) item) acc)))

```
intermediate result
→ ((39 . 35) (33 . 27) (25 . 14) (12 . 11) (8 . 6) (4 . 4) (2 . 0))
2- FORMATTING

(define (range->string range) (let ((from (rest range)) (to (first range))) (cond ((= from to) (format "%d " from)) ((= to (1+ from)) (format "%d, %d " from to)) (else (format "%d-%d " from to)))))

3 - FINAL

(string-join (map range->string (reverse (foldl group-range () task))) ",")

```   → "0-2 ,4 ,6-8 ,11, 12 ,14-25 ,27-33 ,35-39 "
```

</lang>

## Eiffel

<lang Eiffel> class RANGE

create make

feature make local extended_range: STRING do extended_range := "0, 1, 2, 4, 6, 7, 8, 11, 12, 14, " + "15, 16, 17, 18, 19, 20, 21, 22, 23, 24, " + "25, 27, 28, 29, 30, 31, 32, 33, 35, 36, " +

```               		"37, 38, 39"
```

print("Extended range: " + extended_range + "%N") print("Extracted range: " + extracted_range(extended_range) + "%N%N") end

feature extracted_range(sequence: STRING): STRING local elements: LIST[STRING] first, curr: STRING subrange_size, index: INTEGER do sequence.replace_substring_all (", ", ",") elements := sequence.split (',') from index := 2 first := elements.at (1) subrange_size := 0 Result := "" until index > elements.count loop curr := elements.at (index) if curr.to_integer - first.to_integer - subrange_size = 1 then subrange_size := subrange_size + 1 else Result.append(first) if (subrange_size <= 1) then Result.append (", ") else Result.append (" - ") end if (subrange_size >= 1) then Result.append ((first.to_integer + subrange_size).out) Result.append (", ") end

first := curr subrange_size := 0 end index := index + 1 end Result.append(first) if (subrange_size <= 1) then Result.append (", ") else Result.append (" - ") end if (subrange_size >= 1) then Result.append ((first.to_integer + subrange_size).out) end end end </lang>

Output:
```Extended range: 0,  1,  2,  4,  6,  7,  8, 11, 12, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 27, 28, 29, 30, 31, 32, 33, 35, 36, 37, 38, 39
Extracted range: 0 - 2,  4,  6 - 8, 11, 12, 14 - 25, 27 - 33, 35 - 39
```

## Elixir

Translation of: Ruby
```<lang elixir>defmodule RC do
def range_extract(list) do
max = Enum.max(list) + 2
sorted = Enum.sort([max|list])
candidate_number = hd(sorted)
current_number = hd(sorted)
extract(tl(sorted), candidate_number, current_number, [])
end

defp extract([], _, _, range), do: Enum.reverse(range) |> Enum.join(",")
defp extract([next|rest], candidate, current, range) when current+1 >= next do
extract(rest, candidate, next, range)
end
defp extract([next|rest], candidate, current, range) when candidate == current do
extract(rest, next, next, [to_string(current)|range])
end
defp extract([next|rest], candidate, current, range) do
separator = if candidate+1 == current, do: ",", else: "-"
str = "#{candidate}#{separator}#{current}"
extract(rest, next, next, [str|range])
end
```

end

list = [

```  0,  1,  2,  4,  6,  7,  8, 11, 12, 14,
15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
25, 27, 28, 29, 30, 31, 32, 33, 35, 36,
37, 38, 39
```

] IO.inspect RC.range_extract(list)</lang>

Output:
```"0-2,4,6-8,11,12,14-25,27-33,35-39"
```

## Emacs Lisp

### version 1

<lang Emacs Lisp}> (require 'gnus-range) (defun rangext (lst)

``` (mapconcat (lambda (item)
(if (consp item)
```

(if (= (+ 1 (car item) ) (cdr item) ) (format "%d,%d" (car item) (cdr item) ) (format "%d-%d" (car item) (cdr item) ))

```                (format "%d" item)))
(gnus-compress-sequence lst)
","))
```

(insert (rangext '(0 1 2 4 6 7 8 11 12 14

```          15 16 17 18 19 20 21 22 23 24
25 27 28 29 30 31 32 33 35 36
37 38 39) ))
```

</lang>

Output:

```0-2,4,6-8,11,12,14-25,27-33,35-39
```

### version 2

<lang Emacs Lisp}> (setq max-lisp-eval-depth 10000)

(defun ab (a ls)

``` (if ls (if (= (+ a 1) (car ls) )
```

(abc a (car ls) (cdr ls) ) (format "%d,%s" a (ab (car ls) (cdr ls) )))

```   (format "%d" a) ))
```

(defun abc (a b ls)

``` (if ls (if (= (+ b 1) (car ls) )
```

(abcd a (car ls) (cdr ls) ) (format "%d,%d,%s" a b (ab (car ls) (cdr ls) )))

```   (format "%d,%d" a b) ))
```

(defun abcd (a c ls)

``` (if ls (if (= (+ c 1) (car ls) )
```

(abcd a (car ls) (cdr ls) ) (format "%d-%d,%s" a c (ab (car ls) (cdr ls) )))

```   (format "%d-%d" a c) ))
```

(defun rangext (ls)

``` (if ls (ab (car ls) (cdr ls) ) ""))
```

(insert (rangext '(0 1 2 4 6 7 8 11 12 14

```          15 16 17 18 19 20 21 22 23 24
25 27 28 29 30 31 32 33 35 36
37 38 39) ))
```

</lang>

Output:

```0-2,4,6-8,11,12,14-25,27-33,35-39
```

## Erlang

<lang Erlang> -module( range ).

extraction( [H | T] ) when is_integer(H) ->

```       Reversed_extracts = extraction_acc( lists:foldl(fun extraction/2, {H, []}, T) ),
string:join( lists:reverse(Reversed_extracts), "," ).
```

```   io:fwrite( "~p~n", [extraction([0, 1, 2, 4, 6, 7, 8, 11, 12, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 27, 28, 29, 30, 31, 32, 33, 35, 36, 37, 38, 39])] ).
```

extraction( N, {Start, Acc} ) when N =:= Start + 1 -> {Start, N, Acc}; extraction( N, {Start, Acc} ) -> {N, extraction_acc( {Start, Acc} )}; extraction( N, {Start, Stop, Acc} ) when N =:= Stop + 1 -> {Start, N, Acc}; extraction( N, {Start, Stop, Acc} ) -> {N, extraction_acc( {Start, Stop, Acc} )}.

extraction_acc( {N, Acc} ) -> [erlang:integer_to_list(N) | Acc]; extraction_acc( {Start, Stop, Acc} ) when Stop > Start + 1 -> [erlang:integer_to_list(Start) ++ "-" ++ erlang:integer_to_list(Stop) | Acc]; extraction_acc( {Start, Stop, Acc} ) -> [erlang:integer_to_list(Stop), erlang:integer_to_list(Start) | Acc]. % Reversed </lang>

Output:
```19> range:task().
"0-2,4,6-8,11,12,14-25,27-33,35-39"
```

## Euphoria

<lang euphoria>function extract_ranges(sequence s)

```   integer first
sequence out
out = ""
if length(s) = 0 then
return out
end if
first = 1
for i = 2 to length(s) do
if s[i] != s[i-1]+1 then
if first = i-1 then
out &= sprintf("%d,", s[first])
elsif first = i-2 then
out &= sprintf("%d,%d,", {s[first],s[i-1]})
else
out &= sprintf("%d-%d,", {s[first],s[i-1]})
end if
first = i
end if
end for
if first = length(s) then
out &= sprintf("%d", s[first])
elsif first = length(s)-1 then
out &= sprintf("%d,%d", {s[first],s[\$]})
else
out &= sprintf("%d-%d", {s[first],s[\$]})
end if
return out
```

end function

puts(1, extract_ranges({0, 1, 2, 4, 6, 7, 8, 11, 12, 14, 15, 16, 17, 18, 19,

```   20, 21, 22, 23, 24, 25, 27, 28, 29, 30, 31, 32, 33, 35, 36, 37, 38, 39}))</lang>
```
Output:
`0-2,4,6-8,11,12,14-25,27-33,35-39`

## F#

<lang fsharp>let extractRanges = function

``` | []    -> Seq.empty
| x::xr ->
let rec loop ys first last = seq {
match ys with
| y::yr when y = last + 1 -> yield! loop yr first y  // add to current range
| y::yr                   -> yield (first, last)     // finish current range
yield! loop yr y y      //  and start next
| []                      -> yield (first, last) }   // finish final range
loop xr x x
```

let rangeToString (s,e) =

``` match e-s with
| 0 -> sprintf "%d" s
| 1 -> sprintf "%d,%d" s e
| _ -> sprintf "%d-%d" s e
```

let extract = extractRanges >> Seq.map rangeToString >> String.concat ","

printfn "%s" (extract [ 0; 1; 2; 4; 6; 7; 8; 11; 12; 14; 15; 16; 17; 18; 19; 20; 21;

```                       22; 23; 24; 25; 27; 28; 29; 30; 31; 32; 33; 35; 36; 37; 38; 39 ])</lang>
```
Output:
`0-2,4,6-8,11,12,14-25,27-33,35-39`

## Forth

<lang forth>create values here

```   0 ,  1 ,  2 ,  4 ,  6 ,  7 ,  8 , 11 , 12 , 14 ,
15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 ,
25 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 35 , 36 ,
37 , 38 , 39 ,
```

here swap - 1 cells / constant /values

clip 1- swap cell+ swap ; \ reduce array
.range2 0 .r ." -" 0 .r ; \ difference two or more
.range1 0 .r ." , " 0 .r ; \ difference one
.range0 drop 0 .r ; \ no difference
```                                      \ select printing routine
```

create .range ' .range0 , ' .range1 , ' .range2 ,

``` does> >r over over - 2 min cells r> + @ execute ;
```
.ranges ( a n --)
``` over @ dup >r >r                     \ setup first value
begin
clip dup                           \ check length array
while
over @ dup r@ 1+ =                 \ check if range breaks
if r> drop >r else r> r> .range ." , " dup >r >r then
repeat 2drop r> r> .range cr         \ print last range
```

values /values .ranges</lang>

Output:
`0-2, 4, 6-8, 11, 12, 14-25, 27-33, 35-39`

## Fortran

There was some initial confusion as to whether the list was to be supplied as an array of integer values, or as a text string from which integer values were to be extracted. The consensus is a text string. In principle the text string could be parsed to find the starting and stopping positions of each number so that any size integers could be processed merely by copying the texts around without reading the values into integer variables of limited capacity, but that would be complicated by the possible presence of signs. So, it was simpler to take advantage of the free-format data reading protocol that would handle signs without difficulty and on output any spurious +signs would be omitted. This however immediately raises the question: how many numbers are there to be read? A very useful input style is to start with the number of values to read followed by the values; then something like `READ(IN,*) N,A(1:N)` works nicely. But this is not the given style of input, so a fallback: count how many commas appear to deduce how many numbers there are to be read. The free-format style allows either commas or spaces between numbers (and if there is a comma, any spaces also present are passed by), so the layout is easy. Data errors could still be encountered, so a more complete version would have `READ (TEXT,*,ERR=label) VAL(1:N)` to catch these, but the specification does not call for checking.

The standard problem is "how long is a piece of string?" - arrays normally must be given a specific bound. With F90, it is possible to allocate an array of a size determined at run time via some tedious gibberish, but for this example, LOTS will suffice. More seriously, the specification calls for a function returning the text representation of the list, but unfortunately, a function must have a specified size as in `CHARACTER*66 FUNCTION IRANGE(TEXT)` where the 66 is fixed at compile time. With Fortran 2003, there are facilities for the run-time sizing of character variables, but not in F90/95 though they could be devised with a great deal of blather. In any case, the size required is not known until the end, so successively reallocating space of size 1, 2, 3, 4, ... and each time copying the existing text into the larger text area would soon be painful. A largeish value for the size of the result could be used but instead, a subroutine, which returns its result via modifying its parameter. It is up to the caller to provide a parameter of sufficient size.

Although Pascal offers a Str procedure for converting a variable to a text string, maddeningly, it is a procedure not a function and so cannot be used within a compound statement. Fortran could offer access to the FORMAT facility via something like a function FMT(x) which returns the text representation of variable x with no leading or trailing spaces (whereby FMT(-6) would return "-6" and so forth) but alas, does not. Such a function cannot be written in ordinary Fortran until such time as it is possible to return varying-sized character results. The I0 format code standardised in F90 comes close but of course it must be used in a complex environment. All in all, it is easier to devise a subroutine SPLOT(n) to write the value of an integer (with possible leading hyphen if negative) to a scratchpad and then EMIT its text character by character to the output variable character until stopped by a space. Subroutines EMIT and SPLOT could be normal separate subroutines, but as servants of IRANGE it is easier to take advantage of the F90 facility whereby they can be "contained" inside IRANGE and thereby gain access to its internal context. Otherwise, there would have to be additional parameters or usage of COMMON variables for such communication.

The method grinds through the list of values, looking ahead for consecutive continuations (relying on the value of a DO-loop's index variable being available on exit from the loop) and thereby placing in its output string either a range of numbers or a single number. This could be done by using WRITE with suitable FORMAT statements to appropriate portions of the output string via careful counting of positions, but using EMIT and SPLOT avoids the requisite cogitations. A fancier method would be to devise a list of numbers to be output along with a suitable FORMAT statement that would supply the commas and hyphens as appropriate. Of course, one would again face the question "how long is a FORMAT string?", so, grinding stepwise it is. <lang Fortran> SUBROUTINE IRANGE(TEXT) !Identifies integer ranges in a list of integers. Could make this a function, but then a maximum text length returned would have to be specified.

```      CHARACTER*(*) TEXT	!The list on input, the list with ranges on output.
INTEGER LOTS		!Once again, how long is a piece of string?
PARAMETER (LOTS = 666)	!This should do, at least for demonstrations.
INTEGER VAL(LOTS)	!The integers of the list.
INTEGER N		!Count of numbers.
INTEGER I,I1		!Steppers.
N = 1		!Presume there to be one number.
DO I = 1,LEN(TEXT)	!Then by noticing commas,
IF (TEXT(I:I).EQ.",") N = N + 1	!Determine how many more there are.
END DO			!Step alonmg the text.
IF (N.LE.2) RETURN	!One comma = two values. Boring.
IF (N.GT.LOTS) STOP "Too many values!"
READ (TEXT,*) VAL(1:N)	!Get the numbers, with free-format flexibility.
TEXT = ""		!Scrub the parameter!
L = 0			!No text has been placed.
I1 = 1			!Start the scan.
10   IF (L.GT.0) CALL EMIT(",")	!A comma if there is prior text.
CALL SPLOT(VAL(I1))		!The first number always appears.
DO I = I1 + 1,N			!Now probe ahead
IF (VAL(I - 1) + 1 .NE. VAL(I)) EXIT	!While values are consecutive.
END DO				!Up to the end of the remaining list.
IF (I - I1 .GT. 2) THEN		!More than two consecutive values seen?
CALL EMIT("-")		!Yes!
CALL SPLOT(VAL(I - 1))	!The ending number of a range.
I1 = I			!Finger the first beyond the run.
ELSE			!But if too few to be worth a span,
I1 = I1 + 1			!Just finger the next number.
END IF			!So much for that starter.
IF (I.LE.N) GO TO 10	!Any more?
CONTAINS		!Some assistants to save on repetition.
SUBROUTINE EMIT(C)	!Rolls forth one character.
CHARACTER*1 C		!The character.
L = L + 1		!Advance the finger.
IF (L.GT.LEN(TEXT)) STOP "Ran out of text!"	!Maybe not.
TEXT(L:L) = C		!And place the character.
END SUBROUTINE EMIT	!That was simple.
SUBROUTINE SPLOT(N)	!Rolls forth a signed number.
INTEGER N		!The number.
CHARACTER*12 FIELD	!Sufficient for 32-bit integers.
INTEGER I		!A stepper.
WRITE (FIELD,"(I0)") N!Roll the number, with trailing spaces.
DO I = 1,12		!Now transfer the text of the number.
IF (FIELD(I:I).LE." ") EXIT	!Up to the first space.
CALL EMIT(FIELD(I:I))	!One by one.
END DO		!On to the end.
END SUBROUTINE SPLOT	!Not so difficult either.
END	!So much for IRANGE.
```
```     PROGRAM POKE
CHARACTER*(200) SOME
SOME = "  0,  1,  2,  4,  6,  7,  8, 11, 12, 14,  "
1      //"  15, 16, 17, 18, 19, 20, 21, 22, 23, 24,"
2      //"25, 27, 28, 29, 30, 31, 32, 33, 35, 36,  "
3      //"37, 38, 39                               "
CALL IRANGE(SOME)
WRITE (6,*) SOME
END</lang>
```

Output: spaces after the commas could be added easily enough.

` 0-2,4,6-8,11,12,14-25,27-33,35-39`

## FreeBASIC

<lang freebasic>' FB 1.05.0 Win64

Function formatRange (a() As Integer) As String

``` Dim lb As Integer = LBound(a)
Dim ub As Integer = UBound(a)
If ub = - 1 Then Return ""
If lb = ub Then Return Str(a(lb))
Dim rangeCount As Integer = 1
Dim range As String = Str(a(lb))
For i As Integer = lb + 1 To ub
If a(i) = a(i - 1) + 1 Then
rangeCount += 1
ElseIf rangeCount = 1 Then
range += "," + Str(a(i))
ElseIf rangeCount = 2 Then
rangeCount = 1
range += "," + Str(a(i-1)) + "," + Str(a(i))
Else
rangeCount = 1
range += "-" + Str(a(i-1)) + "," + Str(a(i))
End If
Next
If rangeCount = 2 Then
range += "," + Str(a(ub))
ElseIf rangeCount > 2 Then
range += "-" + Str(a(ub))
End If
Return range
```

End Function

Dim a(1 To 20) As Integer = {-6, -3, -2, -1, 0, 1, 3, 4, 5, 7, 8, 9, 10, 11, 14, 15, 17, 18, 19, 20} Print formatRange(a()) Print

Dim b(1 To 33) As Integer => _ { _

```  0,  1,  2,  4,  6,  7,  8, 11, 12, 14, _
15, 16, 17, 18, 19, 20, 21, 22, 23, 24, _
25, 27, 28, 29, 30, 31, 32, 33, 35, 36, _
37, 38, 39 _
```

}

Print formatRange(b()) Print Print "Press any key to continue" Sleep</lang>

Output:
```-6,-3-1,3-5,7-11,14,15,17-20

0-2,4,6-8,11,12,14-25,27-33,35-39
```

## Go

<lang go>package main

import (

```   "errors"
"fmt"
"strconv"
"strings"
```

)

func main() {

```   rf, err := rangeFormat([]int{
0, 1, 2, 4, 6, 7, 8, 11, 12, 14,
15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
25, 27, 28, 29, 30, 31, 32, 33, 35, 36,
37, 38, 39,
})
if err != nil {
fmt.Println(err)
return
}
fmt.Println("range format:", rf)
```

}

func rangeFormat(a []int) (string, error) {

```   if len(a) == 0 {
return "", nil
}
var parts []string
for n1 := 0; ; {
n2 := n1 + 1
for n2 < len(a) && a[n2] == a[n2-1]+1 {
n2++
}
s := strconv.Itoa(a[n1])
if n2 == n1+2 {
s += "," + strconv.Itoa(a[n2-1])
} else if n2 > n1+2 {
s += "-" + strconv.Itoa(a[n2-1])
}
parts = append(parts, s)
if n2 == len(a) {
break
}
if a[n2] == a[n2-1] {
return "", errors.New(fmt.Sprintf(
"sequence repeats value %d", a[n2]))
}
if a[n2] < a[n2-1] {
return "", errors.New(fmt.Sprintf(
"sequence not ordered: %d < %d", a[n2], a[n2-1]))
}
n1 = n2
}
return strings.Join(parts, ","), nil
```

}</lang>

Output:
```range format: 0-2,4,6-8,11,12,14-25,27-33,35-39
```

## Groovy

Ad Hoc Solution: <lang groovy>def range = { s, e -> s == e ? "\${s}," : s == e - 1 ? "\${s},\${e}," : "\${s}-\${e}," }

def compressList = { list ->

```   def sb, start, end
(sb, start, end) = [<<, list[0], list[0]]
for (i in list[1..-1]) {
(sb, start, end) = i == end + 1 ? [sb, start, i] : [sb << range(start, end), i, i]
}
(sb << range(start, end))[0..-2].toString()
```

}

def compressRanges = { expanded -> compressList(Eval.me('[' + expanded + ']')) }</lang>

Test: <lang groovy>def s =

```   0,  1,  2,  4,  6,  7,  8, 11, 12, 14,
15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
25, 27, 28, 29, 30, 31, 32, 33, 35, 36,
37, 38, 39
```

println (compressRanges(s))</lang>

Output:
`0-2,4,6-8,11,12,14-25,27-33,35-39`

extractRange :: [Int] -> String extractRange = intercalate "," . f

``` where f :: [Int] -> [String]
f (x1 : x2 : x3 : xs) | x1 + 1 == x2 && x2 + 1 == x3
= (show x1 ++ '-' : show xn) : f xs'
where (xn, xs') = g (x3 + 1) xs
g a (n : ns) | a == n    = g (a + 1) ns
| otherwise = (a - 1, n : ns)
g a []                   = (a - 1, [])
f (x : xs)            = show x : f xs
f []                  = []</lang>
```

<lang text>> extractRange \$ [0..2] ++ 4 : [6..8] ++ 11 : 12 : [14..25] ++ [27..33] ++ [35..39] "0-2,4,6-8,11,12,14-25,27-33,35-39"</lang>

Or, we can define a reusable splitBy function, which returns a list of lists (split wherever the relationship between two consecutive items matches a supplied predicate function). This allows us a fairly simple simple definition of range formatting:

-- RANGE FORMAT rangeFormat

``` :: (Integral a, Ord a, Show a)
=> [a] -> String
```

rangeFormat = intercalate "," . (rangeString <\$>) . splitBy (\a b -> b - a > 1)

rangeString

``` :: Show a
=> [a] -> String
```

rangeString xs

``` | length xs > 2 = x ++ '-' : last t
| otherwise = intercalate "," ps
where
ps@(x:t) = show <\$> xs
```

-- GENERIC -- Split wherever a supplied predicate matches the relationship -- between two consecutive items splitBy :: (a -> a -> Bool) -> [a] -> a splitBy _ [] = [] splitBy _ [x] = x splitBy f xs@(_:t) = active : acc

``` where
(acc, active) =
foldr
(\(x, prev) (acc, active) ->
if f x prev
then (active : acc, [x])
else ( acc
, x :
if null active
then [prev]
else active))
([], [])
(zip xs t)

```

-- TEST main :: IO () main =

``` print \$
rangeFormat
[ 0, 1, 2, 4, 6, 7, 8, 11, 12, 14,
15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
25, 27, 28, 29, 30, 31, 32, 33, 35, 36,
37, 38, 39]</lang>
```
Output:
`"0-2,4,6-8,11,12,14-25,27-33,35-39"`

## Icon and Unicon

<lang Icon>procedure main()

```  R := [  0,  1,  2,  4,  6,  7,  8, 11, 12, 14,
15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
25, 27, 28, 29, 30, 31, 32, 33, 35, 36,
37, 38, 39 ]
```
```  write("Input list      := ",list2string(R))
write("Extracted sting := ",s := range_extract(R)  | "FAILED")
```

end

procedure range_extract(R) #: return string/range representation of a list of unique integers local s,sep,low,high,x

```  every if integer(x:= !R) ~= x then fail                  # ensure all are integers,
R := sort(set(R))                                        # unique, and sorted
```
```  s := sep := ""
while s ||:= sep || ( low := high := get(R) ) do {       # lower bound of range
sep := ","
while high := ( R[1] = high + 1 ) do get(R)           # find the end of range
if high > low+1 then s ||:= "-" || high               # - record range of 3+
else if high = low+1 then push(R,high)                # - range of 2, high becomes new low
}
return s
```

end

procedure list2string(L) #: helper to convert list to string local s

```  every (s := "[ ") ||:= !L || " "
return s || "]"
```

end</lang>

Output:
```Input list      := [ 0 1 2 4 6 7 8 11 12 14 15 16 17 18 19 20 21 22 23 24 25 27
28 29 30 31 32 33 35 36 37 38 39 ]
Extracted sting := 0-2,4,6-8,11,12,14-25,27-33,35-39```

## J

Older versions of J will also need ` require 'strings'`.

<lang j>fmt=: [: ;@(8!:0) [`]`({. ; (',-' {~ 2 < #) ; {:)@.(2 <. #) group=: <@fmt;.1~ 1 ~: 0 , 2 -~/\ ] extractRange=: ',' joinstring group</lang>

Example use:

<lang j> extractRange 0 1 2 4 6 7 8 11 12 14 15 16 17 18 19 20 21 22 23 24 25 27 28 29 30 31 32 33 35 36 37 38 39 0-2,4,6-8,11,12,14-25,27-33,35-39</lang>

and

<lang j> extractRange (-6, 3, 2, 1), 0, 1, 3, 4, 5, 7, 8, 9, 10, 11, 14, 15, 17, 18, 19, 20 -6,-3-1,3-5,7-11,14,15,17-20</lang>

Other examples:

<lang J> extractRange i.101 0-100</lang>

The first 101 non-negative integers

<lang J>

```  extractRange (-. p:) i.101
```

0,1,4,6,8-10,12,14-16,18,20-22,24-28,30,32-36,38-40,42,44-46,48-52,54-58,60,62-66,68-70,72,74-78,80-82,84-88,90-96,98-100</lang>

Excluding those which are prime

<lang J>

```  extractRange 2}. (-. p:) i.101
```

4,6,8-10,12,14-16,18,20-22,24-28,30,32-36,38-40,42,44-46,48-52,54-58,60,62-66,68-70,72,74-78,80-82,84-88,90-96,98-100</lang>

Also excluding the first two non-negative integers (which are neither prime nor the product of non-empty lists of primes).

## Java

<lang java>public class RangeExtraction {

```   public static void main(String[] args) {
int[] arr = {0, 1, 2, 4, 6, 7, 8, 11, 12, 14,
15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
25, 27, 28, 29, 30, 31, 32, 33, 35, 36,
37, 38, 39};
```
```       int len = arr.length;
int idx = 0, idx2 = 0;
while (idx < len) {
while (++idx2 < len && arr[idx2] - arr[idx2 - 1] == 1);
if (idx2 - idx > 2) {
System.out.printf("%s-%s,", arr[idx], arr[idx2 - 1]);
idx = idx2;
} else {
for (; idx < idx2; idx++)
System.out.printf("%s,", arr[idx]);
}
}
}
```

}</lang>

Output:
`0-2,4,6-8,11,12,14-25,27-33,35-39,`

## JavaScript

### ES5

#### Imperative

<lang javascript>function rangeExtraction(list) {

``` var len = list.length;
var out = [];
var i, j;
```
``` for (i = 0; i < len; i = j + 1) {
// beginning of range or single
out.push(list[i]);

// find end of range
for (var j = i + 1; j < len && list[j] == list[j-1] + 1; j++);
j--;

if (i == j) {
// single number
out.push(",");
} else if (i + 1 == j) {
// two numbers
out.push(",", list[j], ",");
} else {
// range
out.push("-", list[j], ",");
}
}
out.pop(); // remove trailing comma
return out.join("");
```

}

// using print function as supplied by Rhino standalone print(rangeExtraction([

``` 0,  1,  2,  4,  6,  7,  8, 11, 12, 14,
15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
25, 27, 28, 29, 30, 31, 32, 33, 35, 36,
37, 38, 39
```

]));</lang>

#### Functional

Translation of: ES6

<lang JavaScript>(function () {

```   'use strict';
```
```   // rangeFormat :: [Int] -> String
var rangeFormat = function (xs) {
return splitBy(function (a, b) {
return b - a > 1;
}, xs)
.map(rangeString)
.join(',');
};
```
```   // rangeString :: [Int] -> String
var rangeString = function (xs) {
return xs.length > 2 ? [head(xs), last(xs)].map(show)
.join('-') : xs.join(',');
};
```
```   // GENERIC FUNCTIONS
```
```   // Splitting not on a delimiter, but whenever the relationship between
// two consecutive items matches a supplied predicate function
```
```   // splitBy :: (a -> a -> Bool) -> [a] -> a
var splitBy = function (f, xs) {
if (xs.length < 2) return [xs];
lstParts = xs.slice(1)
.reduce(function (a, x) {
var acc = a[0],
active = a[1],
prev = a[2];
```
```               return f(prev, x) ? (
[acc.concat([active]), [x], x]
) : [acc, active.concat(x), x];
}, [
[],
[h], h
]);
return lstParts[0].concat([lstParts[1]]);
};
```
```   // head :: [a] -> a
var head = function (xs) {
return xs.length ? xs[0] : undefined;
};
```
```   // last :: [a] -> a
var last = function (xs) {
return xs.length ? xs.slice(-1)[0] : undefined;
};
```
```   // show :: a -> String
var show = function (x) {
return JSON.stringify(x);
};
```
```   // TEST
return rangeFormat([0, 1, 2, 4, 6, 7, 8, 11, 12, 14, 15, 16,
17, 18, 19, 20, 21, 22, 23, 24, 25, 27, 28, 29, 30, 31, 32,
33, 35, 36, 37, 38, 39
]);
```

})();</lang>

Output:
`"0-2,4,6-8,11,12,14-25,27-33,35-39"`

### ES6

Defining the range format in terms of a reusable splitBy function: <lang JavaScript>(() => {

```   'use strict';
```
```   // rangeFormat :: [Int] -> String
const rangeFormat = xs =>
splitBy((a, b) => b - a > 1, xs)
.map(rangeString)
.join(',');
```
```   // rangeString :: [Int] -> String
const rangeString = xs =>
xs.length > 2 ? (
.join('-')
) : xs.join(',')
```

```   // GENERIC FUNCTIONS
```
```   // Splitting not on a delimiter, but whenever the relationship between
// two consecutive items matches a supplied predicate function
```
```   // splitBy :: (a -> a -> Bool) -> [a] -> a
const splitBy = (f, xs) => {
if (xs.length < 2) return [xs];
const
lstParts = xs.slice(1)
.reduce(([acc, active, prev], x) =>
f(prev, x) ? (
[acc.concat([active]), [x], x]
) : [acc, active.concat(x), x], [
[],
[h],
h
]);
return lstParts[0].concat([lstParts[1]]);
};
```
```   // head :: [a] -> a
const head = xs => xs.length ? xs[0] : undefined;
```
```   // last :: [a] -> a
const last = xs => xs.length ? xs.slice(-1)[0] : undefined;
```
```   // show :: a -> String
const show = x => JSON.stringify(x);
```
```   // TEST
return rangeFormat([0, 1, 2, 4, 6, 7, 8, 11, 12, 14,
15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
25, 27, 28, 29, 30, 31, 32, 33, 35, 36,
37, 38, 39
]);
```

})();</lang>

Output:
`0-2,4,6-8,11,12,14-25,27-33,35-39`

## jq

<lang kq># Input should be an array def extract:

``` reduce .[] as \$i
# state is an array with integers or [start, end] ranges
([];
if length == 0 then [ \$i ]
else ( .[-1]) as \$last
| if (\$last|type) == "array" then
if (\$last[1] + 1) == \$i then setpath([-1,1]; \$i)
else . + [ \$i ]
end
elif (\$last + 1) == \$i then setpath([-1]; [\$last, \$i])
else . + [ \$i ]
end
end)
| map( if type == "number" then tostring
elif .[0] == .[1] -1
then  "\(.[0]),\(.[1])"  # satisfy special requirement
else "\(.[0])-\(.[1])" end )
| join(",") ;</lang>
```
Command and output:
```\$ jq -n -f extract_range.jq input.txt
"0-2,4,6-8,11,12,14-25,27-33,35-39"```

## Julia

This is perhaps an idiosyncratic solution. Numbers inside of runs are replaced with Xs, the list is converted into a comma separated string, and then Xs and extra commas are replaced with the range character via a regular expression. <lang Julia> function sprintfrange{T<:Integer}(a::Array{T,1})

```   len = length(a)
0 < len || return ""
dropme = falses(len)
dropme[2:end-1] = Bool[a[i-1]==a[i]-1 && a[i+1]==a[i]+1 for i in 2:(len-1)]
s = [string(i) for i in a]
s[dropme] = "X"
s = join(s, ",")
replace(s, r",[,X]+,", "-")
```

end

testa = [ 0, 1, 2, 4, 6, 7, 8, 11, 12, 14,

```        15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
25, 27, 28, 29, 30, 31, 32, 33, 35, 36,
37, 38, 39]
```

println("Testing range-style formatting.") println(" ", testa, "\n =>\n ", sprintfrange(testa)) </lang>

Output:
```   [0,1,2,4,6,7,8,11,12,14,15,16,17,18,19,20,21,22,23,24,25,27,28,29,30,31,32,33,35,36,37,38,39]
=>
0-2,4,6-8,11,12,14-25,27-33,35-39
```

## K

<lang k>grp : {(&~1=0,-':x)_ x} fmt : {:[1=#s:\$x;s;(*s),:[3>#s;",";"-"],*|s]} erng: {{x,",",y}/,//'fmt'grp x}</lang>

Example:
```  erng 0 1 2 4 6 7 8 11 12 14 15 16 17 18 19 20 21 22 23 24 25 27 28 29 30 31 32 33 35 36 37 38 39
"0-2,4,6-8,11,12,14-25,27-33,35-39"```

## Liberty BASIC

<lang lb> s\$ = "0, 1, 2, 4, 6, 7, 8, 11, 12, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24," + _

```    "25, 27, 28, 29, 30, 31, 32, 33, 35, 36, 37, 38, 39"
```

print ExtractRange\$( s\$) end

function ExtractRange\$( range\$)

```   n = 1
count = ItemCount( range\$, ",")
while n <= count
startValue = val( word\$( range\$, n, ","))
m = n + 1
while m <= count
nextValue = val( word\$( range\$, m, ","))
if nextValue - startValue <> m - n then exit while
m = m + 1
wend
if m - n > 2 then
ExtractRange\$ = ExtractRange\$ + str\$( startValue) + "-" + str\$( startValue + m - n - 1) + ","
else
for i = n to m - 1
ExtractRange\$ = ExtractRange\$ + str\$( startValue + i - n) + ","
next i
end if
n = m
wend
ExtractRange\$ = left\$( ExtractRange\$, len( ExtractRange\$) - 1)
```

end function

function ItemCount( list\$, separator\$)

```   while word\$( list\$, ItemCount + 1, separator\$) <> ""
ItemCount = ItemCount + 1
wend
```

end function </lang>

Output:
```    0-2,4,6-8,11,12,14-25,27-33,35-39
```

## LiveCode

Inefficient as it takes 2 passes <lang LiveCode>function rangeExtract nums

```   local prevNum, znums, rangedNums
set itemDelimiter to ", "
put the first item of nums into prevNum
repeat for each item n in nums
if n is (prevNum + 1) then
put n into prevNum
put "#" & n after znums
else
put n into prevNum
put return & n after znums
end if
end repeat
set itemDelimiter to "#"
repeat for each line z in znums
if z is empty then next repeat
switch the number of items of z
case 1
put z & "," after rangedNums
break
case 2
put item 1 of z & "," & item -1 of z & "," after rangedNums
break
default
put item 1 of z & "-" & item -1 of z & "," after rangedNums
end switch
end repeat
return char 1 to -2 of rangedNums  --strip off trailing comma
```

end rangeExtract </lang> Test <lang LiveCode>command testRangeExtract

```   local numbers
put "0, 1, 2, 4, 6, 7, 8, 11, 12, 14," \
&& "15, 16, 17, 18, 19, 20, 21, 22, 23, 24," \
&& "25, 27, 28, 29, 30, 31, 32, 33, 35, 36," \
&& "37, 38, 39" into numbers
put rangeExtract(numbers)
```

end testRangeExtract</lang> Output: <lang LiveCode>0-2,4,6-8,11,12,14-25,27-33,35-39</lang>

## Lua

<lang Lua>function extractRange (rList)

```   local rExpr, startVal = ""
for k, v in pairs(rList) do
if rList[k + 1] == v + 1 then
if not startVal then startVal = v end
else
if startVal then
if v == startVal + 1 then
rExpr = rExpr .. startVal .. "," .. v .. ","
else
rExpr = rExpr .. startVal .. "-" .. v .. ","
end
startVal = nil
else
rExpr = rExpr .. v .. ","
end
end
end
return rExpr:sub(1, -2)
```

end

local intList = {

```   0,  1,  2,  4,  6,  7,  8, 11, 12, 14,
15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
25, 27, 28, 29, 30, 31, 32, 33, 35, 36,
37, 38, 39
```

} print(extractRange(intList))</lang>

Output:
`0-2,4,6-8,11,12,14-25,27-33,35-39`

## Mathematica

<lang Mathematica> rangeExtract[data_List] := ToString[Row[

```                              Riffle[
Flatten[Split[Sort[data], #2 - #1 == 1 &] /. {a_Integer, __, b_} :> Row[{a, "-", b}]],
","]
]];
```

</lang>

Example:

```rangeExtract[{0,1,2,4,6,7,8,11,12,14,15,16,17,18,19,20,21,22,23,24,25,27,28,29,30,31,32,33,35,36,37,38,39}]

"0-2,4,6-8,11,12,14-25,27-33,35-39"
```

## MATLAB / Octave

<lang MATLAB>function S=range_extraction(L)

```   % Range extraction
L(end+1) = NaN;
S = int2str(L(1));
k = 1;
while (k < length(L)-1)
if (L(k)+1==L(k+1) && L(k)+2==L(k+2) )
m = 2;
while (L(k)+m==L(k+m))
m = m+1;
end
k = k+m-1;
S = [S,'-',int2str(L(k))];
else
k = k+1;
S = [S,',',int2str(L(k))];
end
end
```

end

disp(range_extraction([0, 1, 2, 4, 6, 7, 8, 11, 12, 14, 15, ...

```                      16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 27, ...
28, 29, 30, 31, 32, 33, 35, 36, 37, 38, 39]))</lang>
```
Output (Octave):
`0-2,4,6-8,11,12,14-25,27-33,35-39`

## MUMPS

<lang MUMPS>RANGCONT(X) ;Integer range contraction

```NEW Y,I,CONT,NOTFIRST,CURR,PREV,NEXT,SEQ SET Y="",SEQ=0,PREV="",CONT=0
FOR I=1:1:\$LENGTH(X,",") DO
.SET NOTFIRST=\$LENGTH(Y),CURR=\$PIECE(X,",",I),NEXT=\$PIECE(X,",",I+1)
.FOR  Q:\$EXTRACT(CURR)'=" "  S CURR=\$EXTRACT(CURR,2,\$LENGTH(CURR))  ;clean up leading spaces
.S SEQ=((CURR-1)=PREV)&((CURR+1)=NEXT)
.IF 'NOTFIRST SET Y=CURR
.IF NOTFIRST DO
..;Order matters due to flags
..IF CONT&SEQ ;Do nothing
..IF 'CONT&'SEQ SET Y=Y_","_CURR
..IF CONT&'SEQ SET Y=Y_CURR,CONT=0
..IF 'CONT&SEQ SET Y=Y_"-",CONT=1
.SET PREV=CURR
IF CONT SET Y=Y_PREV
K I,CONT,NOTFIRST,CURR,PREV,NEXT,SEQ
QUIT Y</lang>
```

Example:

```USER>SET S="0,1,2,4,6,7,8,11,12,14,15,16,17,18,19,20,21,22,23,24,25,27,28,29,30,31,32,33,35,36,37,38,39"

USER>W \$\$RANGCONT^ROSETTA(S)
0-2,4,6-8,11,12,14-25,27-33,35-39```

## NetRexx

### NetRexx Ver. 1

<lang netrexx>/*NetRexx program to test range extraction. ***************************

• 07.08.2012 Walter Pachl derived from my Rexx Version
• Changes: line continuation in aaa assignment changed
• 1e99 -> 999999999
• Do -> Loop
• words(aaa) -> aaa.words()
• word(aaa,i) -> aaa.word(i)
• /

Say 'NetRexx program derived from Rexx' aaa='0 1 2 4 6 7 8 11 12 14 15 16 17 18 19 20 21 22 23 24 25 27 28 29' aaa=aaa' 30 31 32 33 35 36 37 38 39' say 'old='aaa; aaa=aaa 999999999 /* artificial number at the end */ i=0 /* initialize index */ ol= /* initialize output string */ comma= /* will become a ',' lateron */ inrange=0 Loop While i<=aaa.words /* loop for all numbers */

``` i=i+1                             /* index of next number          */
n=aaa.word(i)                     /* the now current number        */
If n=999999999 Then Leave         /* we are at the end             */
If inrange Then Do                /* range was opened              */
If aaa.word(i+1)<>n+1 Then Do   /* following word not in range   */
ol=ol||n                      /* so this number is the end     */
inrange=0                     /* and the range is over         */
End                           /* else ignore current number    */
End
Else Do                           /* not in a range                */
ol=ol||comma||n                 /* add number (with comma)       */
comma=','                       /* to the output string          */
If aaa.word(i+2)=n+2 Then Do    /* if the nr after the next fits */
inrange=1                     /* open a range                  */
ol=ol'-'                      /* append the range connector    */
End
End
End
```

Say 'new='ol</lang>

Output:
```NetRexx program derived from Rexx
old=0 1 2 4 6 7 8 11 12 14 15 16 17 18 19 20 21 22 23 24 25 27 28 29 30 31 32 33 35 36 37 38 39
new=0-2,4,6-8,11,12,14-25,27-33,35-39
```

### NetRexx Ver. 2

Translation of: Java

<lang NetRexx>/* NetRexx */ options replace format comments java crossref symbols nobinary

runSample(arg) return

-- ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ -- Compact a list of numbers by reducing ranges method compact(expanded) public static

``` nums = expanded.changestr(',', ' ').space -- remove possible commas & clean up the string
rezult =
```
``` RANGE = 0
FIRST = nums.word(1) -- set starting value
loop i_ = 2 to nums.words -- each word in the string is a number to examine
LOCAL = nums.word(i_)
if LOCAL - FIRST - RANGE == 1 then do
-- inside a range
RANGE = RANGE + 1
end
else do
-- not inside a range
if RANGE \= 0 then do
-- we have a range of numbers so collect this and reset
rezult = rezult || FIRST || delim(RANGE) || FIRST + RANGE || ','
RANGE = 0
end
else do
-- just collect this number
rezult = rezult || FIRST || ','
end
FIRST = LOCAL -- bump new starting value
end
end i_
```
``` if RANGE \= 0 then do
-- terminating value is a range
rezult = rezult || FIRST || delim(RANGE) || FIRST + RANGE
end
else do
-- terminating value is a single number
rezult = rezult || FIRST
end
```
``` return rezult.space(1, ',') -- format and return result string
```

-- ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ -- determine if the range delimiter should be a comma or dash method delim(range) private static

``` if range == 1 then dlm = ','
else               dlm = '-'
return dlm
```

-- ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ -- sample driver method runSample(arg) public static

parse arg userInput td = 0 if userInput.words > 0 then do

``` -- use input from command line
td[0] = td[0] + 1; r_ = td[0]; td[r_] = userInput
end
```

else do

``` -- use canned test data
td[0] = td[0] + 1; r_ = td[0]; td[r_] = ' -6,  -3,  -2,  -1,   0,   1,   3,  4,  5,   7,  8,  9, 10, 11, 14, 15, 17, 18, 19, 20'
td[0] = td[0] + 1; r_ = td[0]; td[r_] = '  0,   1,   2,   4,   6,   7,   8, 11,  12, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 27, 28, 29, 30, 31, 32, 33, 35, 36, 37, 38, 39'
td[0] = td[0] + 1; r_ = td[0]; td[r_] = ' -4,  -3,  -2,   0,   1,   2,   4,  6,  7,   8, 11, 12, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 27, 28, 29, 30, 31, 32, 33, 35, 36, 37, 38, 39'
end
```

loop r_ = 1 to td[0]

``` say 'Original: ' td[r_].changestr(',', ' ').space(1, ',')
say 'Compacted:' compact(td[r_])
say
end r_
```

return </lang>

Output:
```Original:  -6,-3,-2,-1,0,1,3,4,5,7,8,9,10,11,14,15,17,18,19,20
Compacted: -6,-3-1,3-5,7-11,14,15,17-20

Original:  0,1,2,4,6,7,8,11,12,14,15,16,17,18,19,20,21,22,23,24,25,27,28,29,30,31,32,33,35,36,37,38,39
Compacted: 0-2,4,6-8,11,12,14-25,27-33,35-39

Original:  -4,-3,-2,0,1,2,4,6,7,8,11,12,14,15,16,17,18,19,20,21,22,23,24,25,27,28,29,30,31,32,33,35,36,37,38,39
Compacted: -4--2,0-2,4,6-8,11,12,14-25,27-33,35-39
```

## Nim

<lang nim>import parseutils, re, strutils

proc extractRange(input: string): string =

``` var list = input.replace(re"\s+").split(',').map(parseInt)
var ranges: seq[string] = @[]
var i = 0
while i < list.len:
var first = list[i] # first element in the current range
var offset = i
while True: # skip ahead to the end of the current range
if i + 1 >= list.len:
# reached end of the list
break
if list[i + 1] - (i + 1) != first - offset:
# next element isn't in the current range
break
i.inc
var last = list[i] # last element in the current range
case last - first
i.inc
return ranges.join(",")
```

echo("""

```   0,  1,  2,  4,  6,  7,  8, 11, 12, 14,
15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
25, 27, 28, 29, 30, 31, 32, 33, 35, 36,
37, 38, 39""".extractRange)</lang>
```
Output:
`0-2, 4, 6-8, 11, 12, 14-25, 27-33, 35-39`

## Objeck

Translation of: Java

<lang objeck>class IdentityMatrix {

``` function : Main(args : String[]) ~ Nil {
Compress2Range("-6, -3, -2, -1, 0, 1, 3, 4, 5, 7, 8, 9, 10, 11, 14, 15, 17, 18, 19, 20")->PrintLine();

Compress2Range("0,  1,  2,  4,  6,  7,  8, 11, 12, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 27, 28, 29, 30, 31, 32, 33, 35, 36, 37, 38, 39")->PrintLine();
}

function : Compress2Range(expanded : String) ~ String {
result := "";
nums := expanded->ReplaceAll(" ", "")->Split(",");
firstNum := nums[0]->ToInt();
rangeSize := 0;
for(i:= 1; i < nums->Size(); i += 1;) {
thisNum := nums[i]->ToInt();
if(thisNum - firstNum - rangeSize = 1) {
rangeSize += 1;
}
else{
if(rangeSize <> 0){
result->Append(firstNum);
result->Append((rangeSize = 1) ? ",": "-");
result->Append(firstNum+rangeSize);
result->Append(",");
rangeSize := 0;
}
else {
result->Append(firstNum);
result->Append(",");
};
firstNum := thisNum;
};
};

if(rangeSize <> 0){
result->Append(firstNum);
result->Append((rangeSize = 1) ? "," : "-");
result->Append(firstNum + rangeSize);
rangeSize := 0;
}
else {
result->Append(firstNum);
};

return result;
}
```

} </lang>

## Oberon-2

Oxford Oberon-2 <lang oberon2> MODULE RangeExtraction; IMPORT Out;

PROCEDURE Range(s: ARRAY OF INTEGER); VAR i,j: INTEGER;

PROCEDURE Emit(sep: CHAR); BEGIN IF i > 2 THEN Out.Int(s[j],3);Out.Char('-');Out.Int(s[j + i - 1],3);Out.Char(sep); INC(j,i) ELSE Out.Int(s[j],3);Out.Char(sep); INC(j) END; END Emit;

BEGIN j := 0;i := -1; LOOP INC(i); IF j + i >= LEN(s) THEN Emit(0AX); EXIT ELSIF s[j + i] # (s[j] + i) THEN Emit(','); i := 0; END END END Range;

VAR seq0: ARRAY 33 OF INTEGER; seq1: ARRAY 20 OF INTEGER; BEGIN seq0[0] := 0; seq0[1] := 1; seq0[2] := 2; seq0[3] := 4; seq0[4] := 6; seq0[5] := 7; seq0[6] := 8; seq0[7] := 11; seq0[8] := 12; seq0[9] := 14; seq0[10] := 15; seq0[11] := 16; seq0[12] := 17; seq0[13] := 18; seq0[14] := 19; seq0[15] := 20; seq0[16] := 21; seq0[17] := 22; seq0[18] := 23; seq0[19] := 24; seq0[20] := 25; seq0[21] := 27; seq0[22] := 28; seq0[23] := 29; seq0[24] := 30; seq0[25] := 31; seq0[26] := 32; seq0[27] := 33; seq0[28] := 35; seq0[29] := 36; seq0[30] := 37; seq0[31] := 38; seq0[32] := 39; Range(seq0); seq1[0] := -6; seq1[1] := -3; seq1[2] := -2; seq1[3] := -1; seq1[4] := 0; seq1[5] := 1; seq1[6] := 3; seq1[7] := 4; seq1[8] := 5; seq1[9] := 7; seq1[10] := 8; seq1[11] := 9; seq1[12] := 10; seq1[13] := 11; seq1[14] := 14; seq1[15] := 15; seq1[16] := 17; seq1[17] := 18; seq1[18] := 19; seq1[19] := 20; Range(seq1) END RangeExtraction. </lang>

Output:
```  0-  2,  4,  6-  8, 11, 12, 14- 25, 27- 33, 35- 39
-6, -3-  1,  3-  5,  7- 11, 14, 15, 17- 20
```

## Objective-C

We can use `NSIndexSet` to do this. However, it only works for non-negative integers.

Works with: Mac OS X version 10.7+
Works with: iOS version 5+

<lang objc>#import <Foundation/Foundation.h>

NSString *extractRanges(NSArray *nums) {

``` NSMutableIndexSet *indexSet = [[NSMutableIndexSet alloc] init];
for (NSNumber *n in nums) {
if ([n integerValue] < 0)
@throw [NSException exceptionWithName:NSInvalidArgumentException reason:@"negative number not supported" userInfo:nil];
}
NSMutableString *s = [[NSMutableString alloc] init];
[indexSet enumerateRangesUsingBlock:^(NSRange range, BOOL *stop) {
if (s.length)
[s appendString:@","];
if (range.length == 1)
[s appendFormat:@"%lu", range.location];
else if (range.length == 2)
[s appendFormat:@"%lu,%lu", range.location, range.location+1];
else
[s appendFormat:@"%lu-%lu", range.location, range.location+range.length-1];
}];
return s;
```

}

int main() {

``` @autoreleasepool {
```
```   NSLog(@"%@", extractRanges(@[@0, @1, @2, @4, @6, @7, @8, @11, @12, @14,
@15, @16, @17, @18, @19, @20, @21, @22, @23, @24,
@25, @27, @28, @29, @30, @31, @32, @33, @35, @36,
@37, @38, @39]));
```
``` }
return 0;
```

}</lang>

Output:
```0-2,4,6-8,11,12,14-25,27-33,35-39
```

## OCaml

<lang ocaml>let range_extract = function

``` | [] -> []
| x::xs ->
let f (i,j,ret) k =
if k = succ j then (i,k,ret) else (k,k,(i,j)::ret) in
let (m,n,ret) = List.fold_left f (x,x,[]) xs in
List.rev ((m,n)::ret)
```

let string_of_range rng =

``` let str (a,b) =
if a = b then string_of_int a
else Printf.sprintf "%d%c%d" a (if b = succ a then ',' else '-') b in
String.concat "," (List.map str rng)
```

let () =

``` let li =
[ 0; 1; 2; 4; 6; 7; 8; 11; 12; 14; 15; 16; 17; 18; 19; 20; 21;
22; 23; 24; 25; 27; 28; 29; 30; 31; 32; 33; 35; 36; 37; 38; 39 ]
in
let rng = range_extract li in
print_endline(string_of_range rng)</lang>
```
Output:
`0-2,4,6-8,11,12,14-25,27-33,35-39`

## ooRexx

Translation of: NetRexx Ver. 2
Translation of: Java

<lang ooRexx>/* Rexx */

parse arg userInput call runSample userInput return exit

-- ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ -- Compact a list of numbers by reducing ranges compact: procedure --trace ?r;nop

``` parse arg expanded
nums = expanded~changestr(',', ' ')~space -- remove possible commas & clean up the string
rezult =
```
``` RANGE = 0
FIRST = nums~word(1) -- set starting value
loop i_ = 2 to nums~words -- each word in the string is a number to examine
LOCAL = nums~word(i_)
if LOCAL - FIRST - RANGE == 1 then do
-- inside a range
RANGE += 1
end
else do
-- not inside a range
if RANGE \= 0 then do
-- we have a range of numbers so collect this and reset
rezult = rezult || FIRST || delim(RANGE) || FIRST + RANGE || ','
RANGE = 0
end
else do
-- just collect this number
rezult = rezult || FIRST || ','
end
FIRST = LOCAL -- bump new starting value
end
end i_
if RANGE \= 0 then do
-- collect terminating value (a range)
rezult = rezult || FIRST || delim(RANGE) || FIRST + RANGE
end
else do
-- collect terminating value (a single number)
rezult = rezult || FIRST
end
```
``` return rezult~space(1, ',') -- format and return result string
```

-- ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ -- determine if the range delimiter should be a comma or dash delim: procedure

``` parse arg range .
if range == 1 then dlm = ','
else               dlm = '-'
return dlm
```

-- ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ -- sample driver runSample: procedure parse arg userInput td. = 0 if userInput~words > 0 then do

``` td.0 += 1; r_ = td.0; td.r_ = userInput
end
```

else do

``` td.0 += 1; r_ = td.0; td.r_ = '-6 -3 -2 -1 0 1 3 4 5 7 8 9 10 11 14 15 17 18 19 20'
td.0 += 1; r_ = td.0; td.r_ = '0,  1,  2,  4,  6,  7,  8, 11, 12, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 27, 28, 29, 30, 31, 32, 33, 35, 36, 37, 38, 39'
td.0 += 1; r_ = td.0; td.r_ = '-4, -3, -2, 0, 1, 2, 4, 6, 7, 8, 11, 12, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 27, 28, 29, 30, 31, 32, 33, 35, 36, 37, 38, 39'
end
```

loop r_ = 1 to td.0

``` say 'Original: ' td.r_~changestr(',', ' ')~space(1, ',')
say 'Compacted:' compact(td.r_)
say
end r_
```

return </lang>

Output:
```Original:  -6,-3,-2,-1,0,1,3,4,5,7,8,9,10,11,14,15,17,18,19,20
Compacted: -6,-3-1,3-5,7-11,14,15,17-20

Original:  0,1,2,4,6,7,8,11,12,14,15,16,17,18,19,20,21,22,23,24,25,27,28,29,30,31,32,33,35,36,37,38,39
Compacted: 0-2,4,6-8,11,12,14-25,27-33,35-39

Original:  -4,-3,-2,0,1,2,4,6,7,8,11,12,14,15,16,17,18,19,20,21,22,23,24,25,27,28,29,30,31,32,33,35,36,37,38,39
Compacted: -4--2,0-2,4,6-8,11,12,14-25,27-33,35-39
```

## OxygenBasic

 This example does not show the output mentioned in the task description on this page (or a page linked to from here). Please ensure that it meets all task requirements and remove this message. Note that phrases in task descriptions such as "print and display" and "print and show" for example, indicate that (reasonable length) output be a part of a language's solution.

<lang oxygenbasic>

```  dim sys ints(100)
ints=>
0,  1,  2,  4,  6,  7,  8, 11, 12, 14,
15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
25, 27, 28, 29, 30, 31, 32, 33, 35, 36,
37, 38, 39
```
``` function ShowRange(sys*i) as string
'==================================
pr=""
n=0
e=0
j=0
k=-1
do
j++
n=i(j)
e=i(j+1)
if e<j then
exit do
end if
if e=n+1 and i(j+2)=n+2 then 'LOOKAHEAD
if k=-1 then k=n
else
if k>=0 then
pr+=k "-" i(j+1) ", " 'RANGE OF VALUES
j++
k=-1
else
pr+=n ", " 'SINGLE VALUES
end if
end if
end do
return left pr, len(pr)-2
end function
```

``` print ShowRange ints
```

</lang>

## Oz

<lang oz>declare

``` fun {Extract Xs}
{CommaSeparated
{Map {ExtractRanges Xs} RangeToString}}
end
```
``` fun {ExtractRanges Xs}
fun {Loop Ys Start End}
case Ys
of Y|Yr andthen Y == End+1 then {Loop Yr Start Y}
[] Y|Yr                    then Start#End|{Loop Yr Y Y}
[] nil                     then [Start#End]
end
end
in
case Xs
of X|Xr then {Loop Xr X X}
[] nil then nil
end
end

fun {RangeToString S#E}
if E-S >= 2 then
{VirtualString.toString S#"-"#E}
else
{CommaSeparated
{Map {List.number S E 1} Int.toString}}
end
end
```
``` fun {CommaSeparated Xs}
{Flatten {Intersperse "," Xs}}
end

fun {Intersperse Sep Xs}
case Xs of X|Y|Xr then
X|Sep|{Intersperse Sep Y|Xr}
else
Xs
end
end
```

in

``` {System.showInfo
{Extract [ 0 1 2 4 6 7 8 11 12 14
15 16 17 18 19 20 21 22 23 24
25 27 28 29 30 31 32 33 35 36
37 38 39 ]}}</lang>
```
Output:
`0-2,4,6-8,11,12,14-25,27-33,35-39`

## Pascal

Works with: Free Pascal version 2.6.2

<lang Pascal>program RangeExtraction;

{\$mode objfpc}{\$H+}

uses

``` {\$IFDEF UNIX}{\$IFDEF UseCThreads}
{\$ENDIF}{\$ENDIF}
SysUtils;
```

function RangeExtraction(const Seq: array of integer): String; const

``` SubSeqLen = 3; // minimal length of the range, can be changed.
```

var

``` i, j: Integer;
Separator: string = ;
```

begin

``` Result := ;
i := Low(Seq);
while i <= High(Seq) do
begin
j := i;
// All subsequent values, starting from i, up to High(Seq) possibly
while ((j < High(Seq)) and ((Seq[j+1]-Seq[j]) = 1)) do
Inc(j);
// is it a range ?
if ((j-i) >= (SubSeqLen-1)) then
begin
Result := Result + Format(Separator+'%d-%d',[Seq[i],Seq[j]]);
i := j+1; // Next value to be processed
Separator := ',';
end
else
begin
// Loop, to process the case SubSeqLen > 3
while i<=j do
begin
Result := Result + Format(Separator+'%d',[Seq[i]]);
Inc(i); // Next value to be processed
Separator := ',';
end;
end;
end;
```

End;

procedure DisplayRange(const Seq: array of integer); var

``` i: Integer;
```

begin

``` Write(Format('[%d', [Seq[Low(Seq)]]));
for i := Low(Seq) + 1 to High(Seq) do
Write(Format(',%d', [Seq[i]]));
WriteLn('] => ' + RangeExtraction(Seq));
WriteLn;
```

End;

begin

``` DisplayRange([0]);
DisplayRange([0,1]);
DisplayRange([0,2]);
DisplayRange([0,1,2]);
DisplayRange([0,1,2,3]);
DisplayRange([0,1,2,3,4,5,6,7]);
DisplayRange([0,2,3,4,5,6,7,9]);
DisplayRange([0,2,4,6,8,10]);
DisplayRange([0,1,2,3,4,5,6,7,9]);
DisplayRange([0,1,2,3,4,6,9,10,11,12]);
```
``` DisplayRange([
0,  1,  2,  4,  6,  7,  8, 11, 12, 14,
15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
25, 27, 28, 29, 30, 31, 32, 33, 35, 36,
37, 38, 39]);
```

end. </lang>

Output:
```[0] => 0

[0,1] => 0,1

[0,2] => 0,2

[0,1,2] => 0-2

[0,1,2,3] => 0-3

[0,1,2,3,4,5,6,7] => 0-7

[0,2,3,4,5,6,7,9] => 0,2-7,9

[0,2,4,6,8,10] => 0,2,4,6,8,10

[0,1,2,3,4,5,6,7,9] => 0-7,9

[0,1,2,3,4,6,9,10,11,12] => 0-4,6,9-12

[0,1,2,4,6,7,8,11,12,14,15,16,17,18,19,20,21,22,23,24,25,27,28,29,30,31,32,33,35
,36,37,38,39] => 0-2,4,6-8,11,12,14-25,27-33,35-39```

## Perl

Using regexes. Also handles +/- and negative integer ranges.

<lang Perl>sub rangext {

```   my \$str = join ' ', @_;
1 while \$str =~ s{([+-]?\d+) ([+-]?\d+)}
{\$1.(abs(\$2 - \$1) == 1 ? '~' : ',').\$2}eg; # abs for neg ranges
\$str =~ s/(\d+)~(?:[+-]?\d+~)+([+-]?\d+)/\$1-\$2/g;
\$str =~ tr/~/,/;
return \$str;
```

}

1. Test and display

my @test = qw(0 1 2 4 6 7 8 11 12 14,

```            15 16 17 18 19 20 21 22 23 24,
25 27 28 29 30 31 32 33 35 36,
37 38 39);
```

print rangext(@test), "\n";</lang>

Output:
`0-2,4,6-8,11,12,14-25,27-33,35-39`
Library: Set::IntSpan

<lang Perl>use Set::IntSpan; sub rangext { return Set::IntSpan->new(@_) . } # stringized</lang>

<lang Perl>use Set::IntSpan::Fast; sub rangext { return Set::IntSpan::Fast->new(@_)->as_string }</lang>

`Set::IntSpan` and `Set::IntSpan::Fast` are similar. "Fast" does a binary search for member testing (not part of the task here). Both accept negatives.

## Perl 6

<lang Perl6>sub range-extraction (*@ints) {

```   my \$prev = NaN;
my @ranges;
```
```   for @ints -> \$int {
if \$int == \$prev + 1 {
@ranges[*-1].push: \$int;
}
else {
@ranges.push: [\$int];
}
\$prev = \$int;
}
join ',', @ranges.map: -> @r { @r > 2 ?? "@r[0]-@r[*-1]" !! @r }
```

}

say range-extraction

```   -6, -3, -2, -1, 0, 1, 3, 4, 5, 7, 8, 9, 10, 11, 14, 15, 17, 18, 19, 20;
```

say range-extraction

```   0,  1,  2,  4,  6,  7,  8, 11, 12, 14,
15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
25, 27, 28, 29, 30, 31, 32, 33, 35, 36,
37, 38, 39;</lang>
```
Output:
```-6,-3-1,3-5,7-11,14,15,17-20
0-2,4,6-8,11,12,14-25,27-33,35-39```

## Phix

<lang Phix>function spout(integer first, integer this, sequence s) string res

```   if first=this-1 then
res = sprintf("%d",s[first])
else
res = sprintf("%d%s%d",{s[first],iff(first=this-2?',':'-'),s[this-1]})
end if
return res
```

end function

function extract_ranges(sequence s) integer first = 1 string out = ""

```   if length(s)!=0 then
for i=2 to length(s) do
if s[i]!=s[i-1]+1 then
out &= spout(first,i,s)&','
first = i
end if
end for
out &= spout(first,length(s)+1,s)
end if
return out
```

end function

puts(1,extract_ranges({0,1,2,4,6,7,8,11,12,14,15,16,17,18,19,20,21,22,23,24,25,27,28,29,30,31,32,33,35,36,37,38,39}))</lang>

Output:
```0-2,4,6-8,11,12,14-25,27-33,35-39
```

## PicoLisp

<lang PicoLisp>(de rangeextract (Lst)

```  (glue ","
(make
(while Lst
(let (N (pop 'Lst)  M N)
(while (= (inc M) (car Lst))
(setq M (pop 'Lst)) )
(cond
((= (inc N) M) (link N M))
(T (link (list N '- M))) ) ) ) ) ) )</lang>
```
Output:
```: (rangeextract
(0 1 2 4 6 7 8 11 12 14 15 16 17 18 19 20 21 22
23 24 25 27 28 29 30 31 32 33 35 36 37 38 39 ) )

-> "0-2,4,6-8,11,12,14-25,27-33,35-39"```

## PL/I

<lang pli>/* Modified 19 November 2011 to meet requirement that there be at */ /* least 3 items in a run. */ range_extraction: /* 17 August 2010 */

```  procedure options (main);
declare (c, d) character (1);
declare (old, new, initial) fixed binary (31);
declare in file;
declare out file output;
```
```  open file (in)  title ('/range2.dat,type(text),recsize(80)' );
open file (out) output title ('/range2.out,type(text),recsize(70)');
```
```  c = ' '; d = ',';
get file (in) list (old);
do forever;
initial = old;
on endfile (in) begin;
put file (out) edit (c, trim(old)) (a);
stop;
end;
get file (in) list (new);
if new = old+1 then
do; /* we have a run. */
on endfile (in) begin;
if old > initial+1 then d = '-';
put file (out) edit (c, trim(initial), d, trim(old) ) (a);
stop;
end;
do while (new = old+1);
old = new;
get file (in) list (new);
end;
/* At this point, old holds the last in a run;           */
/* initial holds the first in a run.                     */
/* if there are only two members in a run, don't use the */
/* range notation.                                       */
if old > initial+1 then d = '-';
put file (out) edit (c, trim(initial), d, trim(old) ) (a);
old = new;
end;
else /* we have an isolated value. */
do;
put file (out) edit (c, trim(old)) (a);
old = new;
end;
c, d = ',';
end;
```

end range_extraction;</lang>

OUTPUT 17/8/2010: <lang>

```0-2,4,6-8,11-12,14-25,27-33,35-39
```

</lang>

Output:
``` 0-2,4,6-8,11,12,14-25,27-33,35-39
```

## PowerShell

<lang PowerShell> function range-extraction(\$arr) {

```   if(\$arr.Count -gt 2) {
\$a, \$b, \$c, \$arr = \$arr
\$d = \$e = \$c
if(((\$a + 1) -eq \$b) -and ((\$b + 1) -eq \$c)) {
\$test = \$true
while(\$arr -and \$test) {
\$d = \$e
\$e, \$arr = \$arr
\$test = (\$d+1) -eq \$e
}
if(\$test){"\$a-\$e"}
elseif((-not \$arr) -and \$test){"\$a-\$d"}
elseif(-not \$arr){"\$a-\$d,\$e"}
else{"\$a-\$d," + (range-extraction (@(\$e)+\$arr))}
}
elseif((\$b + 1) -eq \$c) {"\$a," + (range-extraction (@(\$b, \$c)+\$arr))}
else {"\$a,\$b," + (range-extraction (@(\$c)+\$arr))}
} else {
switch(\$arr.Count) {
0 {""}
1 {"\$arr"}
2 {"\$(\$arr[0]),\$(\$arr[1])"}
}
}
```

} range-extraction @(0, 1, 2, 4, 6, 7, 8, 11, 12, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 27, 28, 29, 30, 31, 32, 33, 35, 36, 37, 38, 39) </lang> Output:

```0-2,4,6-8,11,12,14-25,27-33,35-39
```

## Prolog

Works with SWI-Prolog and library clpfd.
The code uses three predicates extract_Range/2, study_Range/2 and pack_Range/2.
Every predicate works in both directions arg1 towards arg2 and arg2 towards arg1, so that Range extraction and Range expansion work with the same predicates but in reverse order. <lang Prolog>range_extract :- L = [0, 1, 2, 4, 6, 7, 8, 11, 12, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 27, 28, 29, 30, 31, 32, 33, 35, 36, 37, 38, 39] , writeln(L), pack_Range(L, LP), maplist(study_Range, R, LP), extract_Range(LA, R), atom_chars(A, LA), writeln(A).

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % extract_Range(?In, ?Out) % In  : '-6,-3--1,3-5,7-11,14,15,17-20' => % Out : [-6], [-3--1], [3-5],[7-11], [14],[15], [17-20] % extract_Range([], []).

extract_Range(X , [Range | Y1]) :- get_Range(X, U-U, Range, X1), extract_Range(X1, Y1).

get_Range([], Range-[], Range, []). get_Range([','|B], Range-[], Range, B) :- !.

get_Range([A | B], EC, Range, R) :- append_dl(EC, [A | U]-U, NEC), get_Range(B, NEC, Range, R).

append_dl(X-Y, Y-Z, X-Z).

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % % study Range(?In, ?Out) % In  : [-6] % Out : [-6,-6] % % In  : [-3--1] % Out : [-3, -1] % study_Range(Range1, [Deb, Deb]) :-

```      catch(number_chars(Deb, Range1), Deb, false).
```

study_Range(Range1, [Deb, Fin]) :-

```      append(A, ['-'|B], Range1),
A \= [],
number_chars(Deb, A),
number_chars(Fin, B).
```

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %

- use_module(library(clpfd)).

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % % Pack Range(?In, ?Out) % In  : -6, % Out : [-6] % % In  : -3, -2,-1 % Out : [-3,-1] % pack_Range([],[]).

pack_Range([X|Rest],[[X | V]|Packed]):-

```   run(X,Rest, [X|V], RRest),
pack_Range(RRest,Packed).
```

run(Fin,[Other|RRest], [Deb, Fin],[Other|RRest]):- Fin #\= Deb, Fin #\= Deb + 1, Other #\= Fin+1.

run(Fin,[],[_Var, Fin],[]).

run(Var,[Var1|LRest],[Deb, Fin], RRest):- Fin #\= Deb, Fin #\= Deb + 1, Var1 #= Var + 1, run(Var1,LRest,[Deb, Fin], RRest).

run(Val,[Other|RRest], [Val, Val],[Other|RRest]). </lang>

Output:
```?- range_extract.
[0,1,2,4,6,7,8,11,12,14,15,16,17,18,19,20,21,22,23,24,25,27,28,29,30,31,32,33,35,36,37,38,39]
0-2,4,6-8,11,12,14-25,27-33,35-39
true```

## PureBasic

Even though the example integer list only includes ascending ranges this code will also handles descending ranges. <lang PureBasic>DataSection

``` Data.i  33 ;count of elements to be read
Data.i  0,  1,  2,  4,  6,  7,  8, 11, 12, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24
Data.i  25, 27, 28, 29, 30, 31, 32, 33, 35, 36, 37, 38, 39
```

EndDataSection

NewList values()

setup list

Define elementCount, i Read.i elementCount For i = 1 To elementCount

``` AddElement(values()): Read.i values()
```

Next

Procedure.s rangeExtract(List values())

``` Protected listSize = ListSize(values()) - 1
Protected rangeMarker, rangeStart, rangeIncrement, retraceSteps, rangeSize, endOfRange, output.s, sub.s

ForEach values()
rangeStart = values():
sub = Str(rangeStart)
If NextElement(values())
retraceSteps = 1
rangeIncrement = values() - rangeStart
If rangeIncrement = 1 Or rangeIncrement = -1
;found start of possible range
If ListIndex(values()) <> listSize
retraceSteps = 2
rangeSize = 2
endOfRange = #False
rangeMarker = values()
While NextElement(values())
If values() - rangeMarker <> rangeIncrement
endOfRange = #True
Break
EndIf
rangeSize + 1
rangeMarker = values()
Wend

If rangeSize > 2
sub = Str(rangeStart) + "-" + Str(rangeMarker)
If Not endOfRange
retraceSteps = 0 ;at end of list
Else
retraceSteps = 1
EndIf
EndIf
EndIf
EndIf

While retraceSteps > 0
PreviousElement(values()): retraceSteps - 1
Wend
EndIf

output + sub + ","
Next

ProcedureReturn RTrim(output, ",")
```

EndProcedure

If OpenConsole()

``` PrintN(rangeExtract(values()))

Print(#CRLF\$ + #CRLF\$ + "Press ENTER to exit")
Input()
CloseConsole()
```

EndIf</lang>

Output:
`0-2,4,6-8,11,12,14-25,27-33,35-39`

## Python

<lang python>def range_extract(lst):

```   'Yield 2-tuple ranges or 1-tuple single elements from list of increasing ints'
lenlst = len(lst)
i = 0
while i< lenlst:
low = lst[i]
while i <lenlst-1 and lst[i]+1 == lst[i+1]: i +=1
hi = lst[i]
if   hi - low >= 2:
yield (low, hi)
elif hi - low == 1:
yield (low,)
yield (hi,)
else:
yield (low,)
i += 1
```

def printr(ranges):

```   print( ','.join( (('%i-%i' % r) if len(r) == 2 else '%i' % r)
for r in ranges ) )
```

if __name__ == '__main__':

```   for lst in [[-8, -7, -6, -3, -2, -1, 0, 1, 3, 4, 5, 7,
8, 9, 10, 11, 14, 15, 17, 18, 19, 20],
[0, 1, 2, 4, 6, 7, 8, 11, 12, 14, 15, 16, 17, 18, 19, 20, 21, 22,
23, 24, 25, 27, 28, 29, 30, 31, 32, 33, 35, 36, 37, 38, 39]]:
#print(list(range_extract(lst)))
printr(range_extract(lst))</lang>
```
Output:
```-8--6,-3-1,3-5,7-11,14,15,17-20
0-2,4,6-8,11,12,14-25,27-33,35-39```
Output:

if the `printr(...)` statement is commented-out instead of the `print(...)` statement directly above it.

This shows the tuples yielded by generator function `range_extract`.

```[(-8, -6), (-3, 1), (3, 5), (7, 11), (14,), (15,), (17, 20)]
[(0, 2), (4,), (6, 8), (11,), (12,), (14, 25), (27, 33), (35, 39)]```

## Qi

<lang qi> (define make-range

``` Start Start -> ["," Start]
Start End   -> ["," Start "," End] where (= End (+ Start 1))
Start End   -> ["," Start "-" End])
```

(define range-extract-0

``` Start End []     -> (make-range Start End)
Start End [A|As] -> (range-extract-0 Start A As) where (= (+ 1 End) A)
Start End [A|As] -> (append (make-range Start End) (range-extract-0 A A As)))
```

(define range-extract

``` [A |As] -> (FORMAT NIL "~{~a~}" (tail (range-extract-0 A A As))))
```

(range-extract [ 0 1 2 4 6 7 8 11 12 14

```               15 16 17 18 19 20 21 22 23 24
25 27 28 29 30 31 32 33 35 36
37 38 39])
```

</lang>

Output:
```0-2,4,6-8,11,12,14-25,27-33,35-39
```

## R

<lang rsplus>extract.range = function(v)

```  {r = c(1, which(diff(v) != 1) + 1, length(v) + 1)
# 'r' holds the index of the start of each run of sequential
# elements.
paste0(collapse = ",", v[head(r, -1)], ifelse(diff(r) == 1, "",
paste0(
ifelse(diff(r) == 2, ",", "-"),
v[r[-1] - 1])))}
```

print(extract.range(c(

```   -6, -3, -2, -1, 0, 1, 3, 4, 5, 7, 8, 9, 10, 11, 14, 15, 17, 18, 19, 20)))
```

print(extract.range(c(

```   0, 1, 2, 4, 6, 7, 8, 11, 12, 14, 15, 16, 17, 18, 19, 20, 21, 22,
23, 24, 25, 27, 28, 29, 30, 31, 32, 33, 35, 36, 37, 38, 39)))</lang>
```

## Racket

<lang Racket>

1. lang racket

(define (list->ranges xs)

``` (define (R lo hi)
(if (= lo hi) (~a lo) (~a lo (if (= 1 (- hi lo)) "," "-") hi)))
(let loop ([xs xs] [lo #f] [hi #f] [r '()])
(cond [(null? xs) (string-join (reverse (if lo (cons (R lo hi) r) r)) ",")]
[(not hi) (loop (cdr xs) (car xs) (car xs) r)]
[(= 1 (- (car xs) hi)) (loop (cdr xs) lo (car xs) r)]
[else (loop xs #f #f (cons (R lo hi) r))])))
```

(list->ranges '(0 1 2 4 6 7 8 11 12 14 15 16 17 18 19 20 21 22 23

```               24 25 27 28 29 30 31 32 33 35 36 37 38 39))
```
-> "0-2,4,6-8,11,12,14-25,27-33,35-39"

</lang>

## REXX

Note that the two numbers   11   and   12   are not considered a range.

### version 1

This REXX version isn't limited to integers. <lang rexx>/*REXX program creates a range extraction from a list of numbers (can be negative.) */ old=0 1 2 4 6 7 8 11 12 14 15 16 17 18 19 20 21 22 23 24 25 27 28 29 30 31 32 33 35 36 37 38 39

1. =words(old) /*number of integers in the number list*/

new= /*the new list, possibly with ranges. */

```    do j=1  to  #;              x=word(old,j)   /*obtain Jth number in the  old  list. */
new=new','  x                               /*append  "    "    to  "   new    "   */
do k=j+1  to #;    y=word(old,k)   /*get the Kth number in the number list*/
if y\==x+inc  then leave           /*is this number not > previous by inc?*/
inc=inc+1;         g=y             /*increase the range, assign  G (good).*/
end   /*k*/
if k-1=j | g=x+1  then iterate              /*Is the range=0│1?  Then keep truckin'*/
new=new'-'g;   j=k-1                        /*indicate a range of #s;  change index*/
end            /*j*/
```

new=space(substr(new, 2), 0) /*elide leading comma, also all blanks.*/ say 'old:' old /*display the old range of numbers. */ say 'new:' new /* " " new list " " */

```                                                /*stick a fork in it,  we're all done. */</lang>
```

output   when using the (internal) list of numbers:

```old: 0 1 2 4 6 7 8 11 12 14 15 16 17 18 19 20 21 22 23 24 25 27 28 29 30 31 32 33 35 36 37 38 39
new: 0-2,4,6-8,11,12,14-25,27-33,35-39
```

### version 1a

The REXX version is the same as above, but doesn't modify a   do   loop's index   (j). <lang rexx>/*REXX program creates a range extraction from a list of numbers (can be negative.) */ old=0 1 2 4 6 7 8 11 12 14 15 16 17 18 19 20 21 22 23 24 25 27 28 29 30 31 32 33 35 36 37 38 39

1. =words(old); j=0 /*number of integers in the number list*/

new= /*the new list, possibly with ranges. */

```    do  while j<#;   j=j+1;     x=word(old,j)   /*get the Jth number in the number list*/
new=new','  x                               /*append  "    "    to  "   new    "   */
do k=j+1  to #;    y=word(old,k)   /*get the Kth number in the number list*/
if y\==x+inc  then leave           /*is this number not > previous by inc?*/
inc=inc+1;         g=y             /*increase the range, assign  G (good).*/
end   /*k*/
if k-1=j | g=x+1  then iterate              /*Is the range=0│1?  Then keep truckin'*/
new=new'-'g;   j=k-1                        /*indicate a range of numbers; change J*/
end            /*while*/
```

new=space(substr(new, 2), 0) /*elide leading comma, also all blanks.*/ say 'old:' old /*display the old range of numbers. */ say 'new:' new /* " " new list " " */

```                                                /*stick a fork in it,  we're all done. */</lang>
```

output   is the same as the 1st REXX version.

### version 2

Somewhat simplified !?! <lang rexx>/*REXX program to test range extraction. ******************************

• 07.08.2012 Walter Pachl
• /

aaa='0 1 2 4 6 7 8 11 12 14 15 16 17 18 19 20 21 22 23 24 25 27 28 29',

```   '30 31 32 33 35 36 37 38 39'
```

say 'old='aaa; aaa=aaa 1e99 /* artificial number at the end */ i=0 /* initialize index */ ol= /* initialize output string */ comma= /* will become a ',' lateron */ inrange=0 Do While i<=words(aaa) /* loop for all numbers */

``` i=i+1                             /* index of next number          */
n=word(aaa,i)                     /* the now current number        */
If n=1e99 Then Leave              /* we are at the end             */
If inrange Then Do                /* range was opened              */
If word(aaa,i+1)<>n+1 Then Do   /* following word not in range   */
ol=ol||n                      /* so this number is the end     */
inrange=0                     /* and the range is over         */
End                           /* else ignore current number    */
End
Else Do                           /* not in a range                */
ol=ol||comma||n                 /* add number (with comma)       */
comma=','                       /* to the output string          */
If word(aaa,i+2)=n+2 Then Do    /* if the nr after the next fits */
inrange=1                     /* open a range                  */
ol=ol'-'                      /* append the range connector    */
End
End
End
```

Say 'new='ol </lang> Output is the same as above.

## Ruby

<lang ruby>def range_extract(l)

``` # pad the list with a big value, so that the last loop iteration will
# append something to the range
sorted, range = l.sort.concat([Float::MAX]), []
canidate_number = sorted.first
```
``` # enumerate over the sorted list in pairs of current number and next by index
sorted.each_cons(2) do |current_number, next_number|
# if there is a gap between the current element and its next by index
if current_number.succ < next_number
# if current element is our first or our next by index
if canidate_number == current_number
# put the first element or next by index into our range as a string
range << canidate_number.to_s
else
# if current element is not the same as the first or next
# add [first or next, first or next equals current add , else -, current]
seperator = canidate_number.succ == current_number ? "," : "-"
range << "%d%s%d" % [canidate_number, seperator, current_number]
end
# make the first element the next element
canidate_number = next_number
end
end
range.join(',')
```

end

lst = [

```   0,  1,  2,  4,  6,  7,  8, 11, 12, 14,
15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
25, 27, 28, 29, 30, 31, 32, 33, 35, 36,
37, 38, 39
```

]

p rng = range_extract(lst)</lang>

Output:
`"0-2,4,6-8,11,12,14-25,27-33,35-39"`

Works with: Ruby version 2.2

Enumerable#slice_when method became usable. <lang ruby>ary = [0,1,2,4,6,7,8,11,12,14,15,16,17,18,19,20,21,22,23,24,25,27,28,29,30,31,32,33,35,36,37,38,39] puts ary.sort.slice_when{|i,j| i+1 != j}.map{|a| a.size<3 ? a : "#{a[0]}-#{a[-1]}"}.join(",")</lang>

Output:
`0-2,4,6-8,11,12,14-25,27-33,35-39`

## Rust

Iterators are very Rustic. This solution is generic for all numeric types. <lang rust>use std::ops::Add;

struct RangeFinder<'a, T: 'a> {

```   index: usize,
length: usize,
arr: &'a [T],
```

}

impl<'a, T> Iterator for RangeFinder<'a, T> where T: PartialEq + Add<u8, Output=T> + Copy {

```   type Item = (T,  Option<T>);
fn next(&mut self) -> Option<Self::Item> {
if self.index == self.length {
return None;
}
let lo = self.index;
while self.index < self.length - 1 && self.arr[self.index + 1] == self.arr[self.index] + 1 {
self.index += 1
}
let hi = self.index;
self.index += 1;
if hi - lo > 1 {
Some((self.arr[lo], Some(self.arr[hi])))
} else {
if hi - lo == 1 {
self.index -= 1
}
Some((self.arr[lo], None))
}
}
```

}

impl<'a, T> RangeFinder<'a, T> {

```   fn new(a: &'a [T]) -> Self {
RangeFinder {
index: 0,
arr: a,
length: a.len(),
}
}
```

}

fn main() {

```   let n = [0,1,2,3];

for (i, (lo, hi)) in RangeFinder::new(&n).enumerate() {
if i > 0 {print!(", ")}
print!("{}", lo);
if hi.is_some() {print!("-{}", hi.unwrap())}
}
println!("");
```

}</lang>

Note: You could make the above solution even a little more generic in Nightly Rust (which is version 1.6 at the time of writing) by making the following additions:

Add this to the top of the file: <lang rust>#![feature(zero_one)] use std::num::One;</lang>

Changing this line: <lang rust> impl<'a, T> Iterator for RangeFinder<'a, T> where T: PartialEq + Add<u8, Output=T> + Copy {</lang> to this: <lang rust>impl<'a, T> Iterator for RangeFinder<'a, T> where T: PartialEq + Add<T, Output=T> + Copy + One {</lang>

And this line: <lang rust> while self.index < self.length - 1 && self.arr[self.index + 1] == self.arr[self.index] + 1 {</lang> to this: <lang rust> while self.index < self.length - 1 && self.arr[self.index + 1] == self.arr[self.index] + T::one() {</lang>

## Scala

<lang scala>object Range {

```  def spanRange(ls:List[Int])={
ls span {x => val b=x<=last+1; last=x; b}
}
```
```  def toRangeList(ls:List[Int]):List[List[Int]]=ls match {
case Nil => List()
case _ => spanRange(ls) match {
case (range, Nil) => List(range)
case (range, rest) => range :: toRangeList(rest)
}
}
```
```  def toRangeString(ls:List[List[Int]])=ls map {r=>
if(r.size<3) r mkString ","
else r.head + "-" + r.last
} mkString ","
```
```  def main(args: Array[String]): Unit = {
var l=List(0, 1, 2, 4, 6, 7, 8, 11, 12, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25,
27, 28, 29, 30, 31, 32, 33, 35, 36, 37, 38, 39)
println(toRangeString(toRangeList(l)))
}
```

}</lang>

Output:
`0-2,4,6-8,11,12,14-25,27-33,35-39`

## Scheme

Translation of: Qi

<lang scheme> (define (make-range start end)

``` (cond ((= start end)
`("," ,start))
((= end (+ start 1))
`("," ,start "," ,end))
(else
`("," ,start "-" ,end))))
```

(define (range-extract-0 start end a)

``` (cond ((null? a)
(make-range start end))
((= (+ 1 end) (car a))
(range-extract-0 start (car a) (cdr a)))
(else
(append (make-range start end)
(range-extract-0 (car a) (car a) (cdr a))))))
```

(define (range-extract a)

``` (apply string-append (map (lambda (x)
(if (number? x)
(number->string x)
x))
(cdr (range-extract-0 (car a) (car a) (cdr a))))))
```

(range-extract '( 0 1 2 4 6 7 8 11 12 14

```                15 16 17 18 19 20 21 22 23 24
25 27 28 29 30 31 32 33 35 36
37 38 39))
```

</lang>

Output:
```0-2,4,6-8,11,12,14-25,27-33,35-39
```

## Seed7

<lang seed7>\$ include "seed7_05.s7i";

const func string: rangeExtraction (in array integer: numbers) is func

``` result
var string: rangeStri is "";
local
var integer: index is 1;
var integer: index2 is 1;
begin
while index <= length(numbers) do
while index2 <= pred(length(numbers)) and numbers[succ(index2)] = succ(numbers[index2]) do
incr(index2);
end while;
if succ(index) < index2 then
rangeStri &:= "," <& numbers[index] <& "-" <& numbers[index2];
else
while index <= index2 do
rangeStri &:= "," <& numbers[index];
incr(index);
```

end while;

```     end if;
incr(index2);
index := index2;
end while;
rangeStri := rangeStri[2 ..];
end func;
```

const proc: main is func

``` begin
writeln(rangeExtraction([] (0, 1, 2, 4, 6, 7, 8, 11, 12, 14, 15, 16, 17, 18, 19,
20, 21, 22, 23, 24, 25, 27, 28, 29, 30, 31, 32, 33, 35, 36, 37, 38, 39)));
end func;</lang>
```
Output:
```0-2,4,6-8,11,12,14-25,27-33,35-39
```

## SNOBOL4

Translation of: Perl
Works with: Macro Spitbol
Works with: CSnobol

Handles +/- and negative ranges.

<lang SNOBOL4>* # Absolute value

```       define('abs(n)') :(abs_end)
```

abs abs = ~(abs = lt(n,0) -n) n :(return) abs_end

```       define('rangext(str)d1,d2') :(rangext_end)
```

rangext num = ('+' | '-' | ) span('0123456789') rxt1 str ',' span(' ') = ' ' :s(rxt1) rxt2 str num . d1 ' ' num . d2 = + d1 ('~,' ? *eq(abs(d2 - d1),1) '~' | ',') d2 :s(rxt2) rxt3 str ('~' | '-') num '~' = '-' :s(rxt3) rxt4 str '~' = ',' :s(rxt4)

```       rangext = str :(return)
```

rangext_end

• # Test and display
```       test =  '0,  1,  2,  4,  6,  7,  8, 11, 12, 14, '
```

+ '15, 16, 17, 18, 19, 20, 21, 22, 23, 24, ' + '25, 27, 28, 29, 30, 31, 32, 33, 35, 36, ' + '37, 38, 39'

```       output = rangext(test)
```

end</lang>

Output:
`0-2,4,6-8,11,12,14-25,27-33,35-39`

## Swift

Works with: Swift version 3

<lang swift> import Darwin

func ranges(from ints:[Int]) -> [(Int, Int)] {

var range : (Int, Int)? var ranges = [(Int, Int)]() for this in ints { if let (start, end) = range { if this == end + 1 { range = (start, this) } else { ranges.append(range!) range = (this, this) } } else { range = (this, this) } } ranges.append(range!)

return ranges }

func description(from ranges:[(Int, Int)]) -> String { var desc = "" for (start, end) in ranges { desc += desc.isEmpty ? "" : "," if start == end { desc += "\(start)" } else if end == start + 1 { desc += "\(start),\(end)" } else { desc += "\(start)-\(end)" } } return desc }

let ex = [-6, -3, -2, -1, 0, 1, 3, 4, 5, 7, 8, 9, 10, 11, 14, 15, 17, 18, 19, 20] let longer = [0, 1, 2, 4, 6, 7, 8, 11, 12, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 27, 28, 29, 30, 31, 32, 33, 35, 36, 37, 38, 39]

print(description(from: ranges(from: ex))) print(description(from: ranges(from: longer))) </lang>

Output:
```-6,-3-1,3-5,7-11,14,15,17-20
0-2,4,6-8,11,12,14-25,27-33,35-39```

## Tcl

<lang tcl>proc rangeExtract list {

```   set result [lindex \$list 0]
set first [set last [lindex \$list 0]]
foreach term [lrange \$list 1 end] {
```

if {\$term == \$last+1} { set last \$term continue } if {\$last > \$first} { append result [expr {\$last == \$first+1 ? "," : "-"}] \$last } append result "," \$term set first [set last \$term]

```   }
if {\$last == \$first+1} {
```

append result "," \$last

```   } elseif {\$last > \$first} {
```

append result "-" \$last

```   }
return \$result
```

}

1. Commas already removed so it is a natural Tcl list

puts [rangeExtract {

```   0 1 2 4 6 7 8 11 12 14
15 16 17 18 19 20 21 22 23 24
25 27 28 29 30 31 32 33 35 36
37 38 39
```

}]</lang>

Output:
`0-2,4,6-8,11,12,14-25,27-33,35-39`

## TXR

<lang txrlisp>(defun range-extract (numbers)

``` `@{(mapcar [iff [callf > length (ret 2)]
(ret `@[@1 0]-@[@1 -1]`)
(ret `@{@1 ","}`)]
(mapcar (op mapcar car)
(split [window-map 1 :reflect
(op list @2 (- @2 @1))
(sort (uniq numbers))]
(op where [chain second (op < 1)])))) ","}`)</lang>
```
Run:
```\$ txr
This is the TXR Lisp interactive listener of TXR 126.
Use the :quit command or type Ctrl-D on empty line to exit.
nil
2> (range-extract '(0 1 2 4 6 7 8 11 12 14 15 16 17 18 19 20 21 22 23 24 25 27 28 29 30 31 32 33 35 36 37 38 39))
"0-2,4,6-8,11,12,14-25,27-33,35-39"```

## TUSCRIPT

TUSCRIPT has a built-in routine "COMBINE" that combines a range of integers by a dash '-'. It is possible to differ between every range that expands more than two values (6-8), and every range that expands less than two values (11,12 are not combined). <lang tuscript> \$\$ MODE TUSCRIPT MODE DATA \$\$ numbers=* 0, 1, 2, 4, 6, 7, 8, 11, 12, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 27, 28, 29, 30, 31, 32, 33, 35, 36, 37, 38, 39 \$\$ MODE TUSCRIPT numbers=EXCHANGE (numbers,":,><<> :':") unrangednrs=JOIN (numbers,"") rangednrs=COMBINE (unrangednrs,"") rangednrs=EXCHANGE (rangednrs,":':,:") PRINT rangednrs </lang>

Output:
```0-2,4,6-8,11,12,14-25,27-33,35-39
```

Solution without COMBINE <lang tuscript> \$\$ MODE TUSCRIPT MODE DATA \$\$ numbers=* 0, 1, 2, 4, 6, 7, 8, 11, 12, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 27, 28, 29, 30, 31, 32, 33, 35, 36, 37, 38, 39 \$\$ MODE TUSCRIPT numbers=EXCHANGE (numbers,":,><<> :':") unrangednrs=JOIN (numbers,"")

help = APPEND (unrangednrs, "999999999") rest = REMOVE (help, 1, n_1) n_2 = n_1, n_3= n_2 + 1,rangednrs= "" LOOP n= rest

```IF (n!=n_3)  THEN
rangednrs = APPEND (rangednrs, n_1)
IF (n_1!=n_2) THEN
range=n_1+1
IF (range==n_2) THEN
rangednrs = APPEND (rangednrs,n_2)
ELSE
rangednrs = CONCAT (rangednrs, "-", n_2)
ENDIF
ENDIF
n_1 = n
ENDIF
n_2 = n, n_3 = n_2 + 1
```

ENDLOOP rangednrs=EXCHANGE (rangednrs,":':,:") PRINT rangednrs </lang>

Output:
```0-2,4,6-8,11,12,14-25,27-33,35-39
```

## UNIX Shell

Works with: bash

<lang bash>#!/usr/bin/bash

range_contract () (

```   add_range () {
case \$(( current - range_start )) in
0) ranges+=( \$range_start )          ;;
1) ranges+=( \$range_start \$current ) ;;
*) ranges+=("\$range_start-\$current") ;;
esac
}
```
```   ranges=()
range_start=\$1
current=\$1
shift
```
```   for number; do
if (( number > current+1 )); then
range_start=\$number
fi
current=\$number
done
```
```   x="\${ranges[@]}"
echo \${x// /,}
```

)

range_contract 0 1 2 4 6 7 8 11 12 14 15 16 17 18 19 20 21 22 23 24 25 27 28 29 30 31 32 33 35 36 37 38 39</lang>

Output:
`0-2,4,6-8,11,12,14-25,27-33,35-39`

## Ursala

<lang Ursala>#import std

1. import int

x = <0,1,2,4,6,7,8,11,12,14,15,16,17,18,19,20,21,22,23,24,25,27,28,29,30,31,32,33,35,36,37,38,39>

f = mat`,+ ==?(~&l,^|T/~& :/`-)*bhPS+ %zP~~hzX*titZBPiNCSiNCQSL+ rlc ^|E/~& predecessor

1. show+

t = <f x></lang>

Output:
`0-2,4,6-8,11,12,14-25,27-33,35-39`

## VBA

<lang vb> Public Function RangeExtraction(AList) As String 'AList is a variant that is an array, assumed filled with numbers in ascending order Const RangeDelim = "-" 'range delimiter Dim result As String Dim InRange As Boolean Dim Posn, ub, lb, rangestart, rangelen As Integer

result = "" 'find dimensions of AList ub = UBound(AList) lb = LBound(AList) Posn = lb While Posn < ub

``` rangestart = Posn
rangelen = 0
InRange = True
'try to extend the range
While InRange
rangelen = rangelen + 1
If Posn = ub Then
InRange = False
Else
InRange = (AList(Posn + 1) = AList(Posn) + 1)
Posn = Posn + 1
End If
Wend
If rangelen > 2 Then 'output the range if it has more than 2 elements
result = result & "," & Format\$(AList(rangestart)) & RangeDelim & Format\$(AList(rangestart + rangelen - 1))
Else 'output the separate elements
For i = rangestart To rangestart + rangelen - 1
result = result & "," & Format\$(AList(i))
Next
End If
Posn = rangestart + rangelen
```

Wend RangeExtraction = Mid\$(result, 2) 'get rid of first comma! End Function

Public Sub RangeTest() 'test function RangeExtraction 'first test with a Variant array Dim MyList As Variant MyList = Array(0, 1, 2, 4, 6, 7, 8, 11, 12, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 27, 28, 29, 30, 31, 32, 33, 35, 36, 37, 38, 39) Debug.Print "a) "; RangeExtraction(MyList)

'next test with an array of integers Dim MyOtherList(1 To 20) As Integer MyOtherList(1) = -6 MyOtherList(2) = -3 MyOtherList(3) = -2 MyOtherList(4) = -1 MyOtherList(5) = 0 MyOtherList(6) = 1 MyOtherList(7) = 3 MyOtherList(8) = 4 MyOtherList(9) = 5 MyOtherList(10) = 7 MyOtherList(11) = 8 MyOtherList(12) = 9 MyOtherList(13) = 10 MyOtherList(14) = 11 MyOtherList(15) = 14 MyOtherList(16) = 15 MyOtherList(17) = 17 MyOtherList(18) = 18 MyOtherList(19) = 19 MyOtherList(20) = 20 Debug.Print "b) "; RangeExtraction(MyOtherList) End Sub </lang>

Output:
```RangeTest
a) 0-2,4,6-8,11,12,14-25,27-33,35-39
b) -6,-3-1,3-5,7-11,14,15,17-20
```

## VBScript

<lang vb>Function Range_Extraction(list) num = Split(list,",") For i = 0 To UBound(num) startnum = CInt(num(i)) sum = startnum Do While i <= UBound(num) If sum = CInt(num(i)) Then If i = UBound(num) Then If startnum <> CInt(num(i)) Then If startnum + 1 = CInt(num(i)) Then Range_Extraction = Range_Extraction & startnum & "," & num(i) & "," Else Range_Extraction = Range_Extraction & startnum & "-" & num(i) & "," End If Else Range_Extraction = Range_Extraction & startnum & "," End If

```                                       Exit Do
```

Else i = i + 1 sum = sum + 1 End If Else If startnum = CInt(num(i-1)) Then Range_Extraction = Range_Extraction & startnum & "," Else If startnum + 1 = CInt(num(i-1)) Then Range_Extraction = Range_Extraction & startnum & "," & num(i-1) & "," Else Range_Extraction = Range_Extraction & startnum & "-" & num(i-1) & "," End If End If i = i - 1 Exit Do End If Loop Next Range_Extraction = Left(Range_Extraction,Len(Range_Extraction)-1) End Function

WScript.StdOut.Write Range_Extraction("0,1,2,4,6,7,8,11,12,14,15,16,17,18,19,20,21,22,23,24,25,27,28,29,30,31,32,33,35,36,37,38,39")</lang>

Output:
`0-2,4,6-8,11,12,14-25,27-33,35-39`

## zkl

<lang zkl>fcn range(ns){

```  fcn(w){
if (w.atEnd) return(Void.Stop);
a:=b:=w.next(); n:=0;
while(b+1 == (c:=w.peekN(n))){ n+=1; b=c }
if(n>1){do(n){w.next()}; return("%d-%d".fmt(a,b)); }
a
} :
(0).pump(*,List,_.fp(ns.walker().tweak(Void,Void))).concat(",");
```

}</lang> The trick here is to use a modified iterator, one that can look past the end of the sequence without puking. The function gathers three or more successive ints (saved as a "a-b" string list element) or just returns the first one (as a number) if it can't. The resulting list is converted to strings separated by commas. <lang zkl>var ns=T(-6,-3,-2,-1,0,1,3,4,5,7,8,9,10,11,14,15,17,18,19,20); range(ns).println();

ns=T(

```   0,  1,  2,  4,  6,  7,  8, 11, 12, 14,
15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
25, 27, 28, 29, 30, 31, 32, 33, 35, 36,
37, 38, 39);
```

range(ns).println();

range([1..100]).println();</lang>

Output:
```-6,-3-1,3-5,7-11,14,15,17-20
0-2,4,6-8,11,12,14-25,27-33,35-39
1-100
```