# Kernighans large earthquake problem

Kernighans large earthquake problem
You are encouraged to solve this task according to the task description, using any language you may know.

Brian Kernighan, in a lecture at the University of Nottingham, described a problem on which this task is based.

Problem

You are given a a data file of thousands of lines; each of three `whitespace` separated fields: a date, a one word name and the magnitude of the event.

Example lines from the file would be lines like:

```8/27/1883    Krakatoa            8.8
5/18/1980    MountStHelens       7.6
3/13/2009    CostaRica           5.1```
• Create a program or script invocation to find all the events with magnitude greater than 6
• Assuming an appropriate name e.g. "data.txt" for the file:
1. Either: Show how your program is invoked to process a data file of that name.
2. Or: Incorporate the file name into the program, (as it is assumed that the program is single use).

## 11l

Translation of: Python
```L(ln) File(‘data.txt’).read_lines()
I Float(ln.split(‘ ’, group_delimiters' 1B)[2]) > 6
print(ln)```
Output:
```8/27/1883    Krakatoa            8.8
5/18/1980    MountStHelens       7.6
```

## 68000 Assembly

I'm going to make the assumption that all magnitudes are given as floating points rounded to one decimal place, e.g. "6.0" when the magnitude is exactly 6. That way I don't need to actually use floating point logic. The hardware print routines were omitted to keep things short, since the Sega Genesis doesn't have a built-in kernel and so I'd have to manually write to the video chip. Chances are you're not interested in seeing all that fluff when you'd rather look at the actual algorithm for the task.

```;Macros
macro pushRegs 1
MOVEM.L \1,-(SP)
endm
;---------------------------------------------------------------------------
macro popRegs 1
MOVEM.L (SP)+,\1
endm
;---------------------------------------------------------------------------

;Ram Variables
ramArea equ \$00FF0000
Cursor_X equ ramArea	;Ram for Cursor Xpos
Cursor_Y equ ramArea+1	;Ram for Cursor Ypos

;cartridge header and init routine go here, I'll leave them out to keep things short. Execution falls through into here
;after the screen has been activated and the bitmap font loaded into VRAM

LEA earthquake,A3
move.l #3-1,d7			;total line count in the file.
mainloop:
MOVE.B #'.',D0			;find the period in each line.
MOVE.B #10,D1
jsr CharInThisLine
CMP.B #255,D0
BNE foundIt
jsr lineseek
jmp mainloop
foundIt:
;print only if magnitude is 6.1 or greater
suba.l #2,a4
cmp.b #'6',(a4)
bcs .skip
cmp.b #'0',(a4)
beq .skip
jsr printline
.skip:
DBRA D7,mainloop

jmp *						;end program

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; unixdict functions:
PrintLine:
MOVE.B (A3)+,D0
CMP.B #10,D0
BEQ .done
CMP.B #255,D0
BEQ .done
jsr PrintChar
bra PrintLine
.done:
ADDA.L #1,A0 ;inc past the line feed to the next word.
;fallthrough is intentional here
NewLine:
clr.b (Cursor_X)		;Zero X
rts
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
IgnoreCase:
;forces lower case.
;input: d0.b
;output: d0.b
CMP.B #'A',D0       ;compare to ascii code for A
BCS .done      		;if less than A, keep looping.

CMP.B #'Z'+1,D0       ;compare to ascii code for Z
BCC .done      		;if greater than Z, keep looping

OR.B #%00100000,D0  ;this "magic constant" turns upper case to lower case, since they're always 32 apart.
.done
RTS
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
CharInThisLine:
pushregs d2-d4/a3
;input: d0 = char to search for. d1 = terminator of choice
MOVEQ #0,D3
.again:
MOVE.B (A3)+,D2
CMP.B D1,D2
BEQ .didntFindIt
pushlong d0
move.b d2,d0
jsr ignoreCase
move.b d0,d2
poplong d0
CMP.B D0,D2
BEQ .foundIt
bra .again

.didntFindIt:
MOVE.B #255,D0		;RETURN 255 ON FAILURE
bra .exit
.foundIt:
MOVE.L D3,D0		;RETURN ZERO-INDEXED POSITION OF CHAR ON SUCCESS
bra .exit

.exit:
move.l a3,a4
popregs d2-d4/a3
rts
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
lineseek:
;advances pointer to the "next" word without printing anything.
MOVE.B (A3)+,D0
CMP.B #10,D0
BEQ .done
CMP.B #255,D0
BEQ .done
bra lineseek
.done:
RTS```
Output:
```8/27/1883    Krakatoa            8.8
5/18/1980    MountStHelens       7.6```

## 8080 Assembly

Say what you want about language design, but assembly does let you cut down the work done to the absolute minimum. This program can process a file of arbitrary size on a machine from the 1970s about as quickly as the disk can supply the bytes, needing no more working memory than the size of one line plus four bytes of stack space.

The file is given on the command line, because that way CP/M will set up an FCB automatically.

```FCB1:	equ	5Ch	; FCB for first command line argument
puts:	equ	9	; CP/M syscall to print a string
fopen:	equ	15	; CP/M syscall to open a file
fread:	equ	20	; CP/M syscall to read a block from a file
dta:	equ	80h	; Default disk transfer address
org	100h
lxi	d,FCB1	; Try to open the file given on the command line
mvi	c,fopen
call	5
inr	a	; A = 0 = error
jz	err
lxi	h,line	; Start of line buffer
block:	push	h	; Keep line buffer pointer
lxi	d,FCB1	; Read a block from the file
call	5
pop	h	; Restore line buffer pointer
dcr	a	; A = 1 = end of file (done)
rz
inr	a	; otherwise, A <> 0 = read error
jnz	err
lxi	d,dta	; Start of block
char:	ldax	d	; Grab character from block
mov	m,a	; Store in line buffer
inx	h	; Advance line buffer pointer
cpi	10	; End of line?
cz	doline	; Then handle the line
inr	e	; Next character in block
jz	block	; Rollover = get new block
jmp	char 	; Otherwise = get next char
;;;	Handle a line
doline:	push	d	; Keep block pointer
mvi	m,'\$'	; Terminate line buffer with CP/M end-of-string marker
mvi	a,32
scan1:	dcx	h	; Scan backwards from end of line until we find
cmp	m	; a non-control/whitespace character
jnc	scan1	; (this makes it newline-format agnostic)
scan2:	dcx	h	; Then scan backwards until we _do_ find whitespace
cmp	m	; This should leave us pointing right before the number
jc	scan2
inx	h	; First digit - we can cheat a little since we know
mov	a,m	; earthquakes >=10 are physically impossible
cpi	'7'	; If 7 or larger we know we should print it
jnc	print
cpi	'6' 	; If smaller than 6 we know we mustn't print it
jc	next
inx	h	; If 6, we must check fractional part
mov	a,m
cpi	'.'	; If no fractional part, then it is exactly 6 so
jnz	next	; we shouldn't print it
scan3:	inx	h
mov	a,m
cpi	'\$'	; If we reach the end, don't print it
jz	next
cpi	'1' 	; But if fractional part > 0, do print it
jc	scan3
print:	lxi	d,line	; Print the line
mvi	c,puts
call	5
next:	pop	d	; Restore block pointer
lxi	h,line	; Put line buffer pointer back at beginning
ret
err:	lxi	d,emsg	; Print error message and stop
mvi	c,puts
jmp	5
emsg:	db	'Error!\$'
line:	equ	\$	; Line buffer after program```
Output:
```A>type data.txt
8/27/1883    Krakatoa            8.8
5/18/1980    MountStHelens       7.6
3/13/2009    CostaRica           5.1
1/23/4567    EdgeCase1           6
1/24/4567    EdgeCase2           6.0
1/25/4567    EdgeCase3           6.1

A>quakes data.txt
8/27/1883    Krakatoa            8.8
5/18/1980    MountStHelens       7.6
1/25/4567    EdgeCase3           6.1
```

## Action!

In the following solution the input file quakes.txt is loaded from H6 drive. Altirra emulator automatically converts CR/LF character from ASCII into 155 character in ATASCII charset used by Atari 8-bit computer when one from H6-H10 hard drive under DOS 2.5 is used.

```INCLUDE "H6:REALMATH.ACT"

BYTE FUNC FindFirstNonspace(CHAR ARRAY s BYTE start)
WHILE start<=s(0) AND s(start)=32
DO
start==+1
OD
RETURN (start)

BYTE FUNC FindFirstSpace(CHAR ARRAY s BYTE start)
WHILE start<=s(0) AND s(start)#32
DO
start==+1
OD
RETURN (start)

BYTE FUNC Found(CHAR ARRAY s REAL POINTER value)
BYTE pos,v
CHAR ARRAY sub

pos=FindFirstNonspace(s,1)
pos=FindFirstSpace(s,pos)
pos=FindFirstNonspace(s,pos)
pos=FindFirstSpace(s,pos)
pos=FindFirstNonspace(s,pos)
IF pos>s(0) THEN RETURN (0) FI

SCopyS(sub,s,pos,s(0))
ValR(sub,v)
IF RealGreaterOrEqual(value,v)=0 THEN
RETURN (1)
FI
RETURN (0)

PROC Process(CHAR ARRAY fname REAL POINTER value BYTE search)
CHAR ARRAY line(255)
BYTE dev=[1]

Close(dev)
Open(dev,fname,4)
WHILE Eof(dev)=0
DO
InputSD(dev,line)
IF search=0 OR Found(line,value)=1 THEN
PrintE(line)
FI
OD
Close(dev)
RETURN

PROC Main()
CHAR ARRAY fname="H6:QUAKES.TXT"
REAL value

Put(125) PutE() ;clear the screen
IntToReal(6,value)
Process(fname,value,0)
PutE()
Print("Searching for earthquakes > ")
PrintRE(value) PutE()
Process(fname,value,1)
RETURN```
Output:
```Reading "H6:QUAKES.TXT"...

8/27/1883    Krakatoa            8.8
5/18/1980    MountStHelens       7.6
3/13/2009    CostaRica           5.1
1/23/4567    EdgeCase1           6

1/24/4567    EdgeCase2           6.0
1/25/4567    EdgeCase3           6.1

Searching for earthquakes > 6

8/27/1883    Krakatoa            8.8
5/18/1980    MountStHelens       7.6
1/25/4567    EdgeCase3           6.1
```

```-- Kernighans large earthquake problem

procedure Main is
Inpt_File : File_Type;
Space     : Natural;
begin
Open (File => Inpt_File, Mode => In_File, Name => "data.txt");
while not End_Of_File (Inpt_File) loop
declare
Line : String :=
Trim (Source => Get_Line (File => Inpt_File), Side => Both);
begin

if Line'Length > 0 then
Space := Line'Last;
loop
exit when Line (Space) = ' ' or else Space = 0;
Space := Space - 1;
end loop;

if Space > 0 then
if Float'Value (Line (Space .. Line'Last)) > 6.0 then
Put_Line (Line);
end if;
end if;
end if;
end;
end loop;
Close (Inpt_File);
end Main;
```

The file data.txt contains a 0 length line as well as a line composed of only blanks.

```8/27/1883    Krakatoa            8.8
5/18/1980    MountStHelens       7.6
3/13/2009    CostaRica           5.1
1/23/4567    EdgeCase1           6

1/24/4567    EdgeCase2           6.0
1/25/4567    EdgeCase3           6.1
```
Output:
```8/27/1883    Krakatoa            8.8
5/18/1980    MountStHelens       7.6
1/25/4567    EdgeCase3           6.1
```

## ALGOL 68

```IF  FILE input file;
STRING file name = "data.txt";
open( input file, file name, stand in channel ) /= 0
THEN
# failed to open the file #
print( ( "Unable to open """ + file name + """", newline ) )
ELSE
# file opened OK #
BOOL at eof := FALSE;
# set the EOF handler for the file #
on logical file end( input file, ( REF FILE f )BOOL:
BEGIN
# note that we reached EOF on the latest read #
at eof := TRUE;
# return TRUE so processing can continue #
TRUE
END
);
# return the real value of the specified field on the line #
PROC real field = ( STRING line, INT field )REAL:
BEGIN
REAL result  := 0;
INT  c pos   := LWB line;
INT  max pos := UPB line;
STRING f     := "";
FOR f ield number TO field WHILE c pos <= max pos DO
WHILE IF c pos > max pos THEN FALSE ELSE line[ c pos ] = " " FI DO
c pos +:= 1
OD;
IF c pos <= max pos THEN
# have a field #
INT start pos = c pos;
WHILE IF c pos > max pos THEN FALSE ELSE line[ c pos ] /= " " FI DO
c pos +:= 1
OD;
IF field number = field THEN
# have the required field #
f := line[ start pos : c pos - 1 ]
FI
FI
OD;
IF f /= "" THEN
# have the field - assume it a real value and convert it #
FILE real value;
associate( real value, f );
on value error( real value
, ( REF FILE f )BOOL:
BEGIN
# "handle" invalid data #
result := 0;
# return TRUE so processing can continue #
TRUE
END
);
get( real value, ( result ) )
FI;
result
END # real field # ;
# show the lines where the third field is > 6 #
WHILE NOT at eof
DO
STRING line;
get( input file, ( line, newline ) );
IF real field( line, 3 ) > 6 THEN
print( ( line, newline ) )
FI
OD;
# close the file #
close( input file )
FI```

## Amazing Hopper

```/* Kernighans large earthquake problem. */

#include <flow.h>
#include <flow-flow.h>

#define MAX_LINE 1000

DEF-MAIN(argv,argc)
MSET(fd, Event )
TOK-INIT
OPEN-INPUT("datos.txt")(fd)
COND( IS-NOT-FILE-ERROR? )
TOK-SEP( " " ), TOK(3)
WHILE( NOT( EOF(fd) ) )
LET( Event := USING(MAX_LINE) READ-LINE(fd) APPLY-TRM )
WHEN( LEN(Event) ){
WHEN( GT?( VAL(TOK-GET(Event)), 6 ) ){
PRNL( Event )
}
}
WEND
CLOSE(fd)
ELS
PRNL("Error: ", ~GET-STR-FILE-ERROR )
CEND
END```
Output:
```Data file: datos.txt.

8/27/1883    Krakatoa            8.8
5/18/1980    MountStHelens       7.6
3/13/2009    CostaRica           5.1
1/23/4567    EdgeCase1           6

1/24/4567    EdgeCase2           6.0
1/25/4567    EdgeCase3           6.1
```

Output:

```\$ hopper fl/evento.flw
8/27/1883    Krakatoa            8.8
5/18/1980    MountStHelens       7.6
1/25/4567    EdgeCase3           6.1
\$
```

PROBLEM: What if the file contains more information than expected? We would have to validate the lines that can be processed. For example, we might have a file with the following information:

```8/27/1883    Krakatoa            8.8
5/18/1980    MountStHelens       7.6
3/13/2009    CostaRica           5.1
Total events: 3

1/23/4567    EdgeCase1           6

1/24/4567    EdgeCase2           6.0
1/25/4567    EdgeCase3           6.1
1/25/4567    EdgeCase4           6.1
Total events: 4

Total Events in periods: 7
```

There are lines with 3 tokens, and the third token is numeric: it would be shown as a valid record!

On the other hand, HOPPER processes dates in DD/MM/YYYY format, and the file records dates in MM/DD/YYYY format: therefore, it is necessary to exchange "DD" for "MM", because HOPPER does not allow other types of format for "dates".

The final program would be as follows:

```/* Kernighans large earthquake problem. */

#include <flow.h>
#include <flow-flow.h>

#define MAX_LINE                  1000
#define SwapDayByMonth(_N_,_M_)   TOK-SEP("/"), TOK(_N_), TOK-SWAP(_M_,Event), TOK-SEP(" ")

DEF-MAIN(argv,argc)
MSET(fd, Event )
TOK-INIT
OPEN-INPUT("datos.txt")(fd)
COND( IS-NOT-FILE-ERROR? )
TOK-SEP( " " )
WHILE( NOT( EOF(fd) ) )
LET( Event := USING(MAX_LINE) READ-LINE(fd) APPLY-TRM )
WHEN( LEN(Event) ){
WHEN( EQ?(TOK-COUNT( Event ),3) ){
Swap Day By Month(1,2)
WHEN( IS-DATE-VALID?( TOK(1) TOK-GET(Event) )){
TOK(3)
WHEN( GT?( VAL(TOK-GET(Event)), 6 ) ){
PRNL( Event )
}
}
}
}
WEND
CLOSE(fd)
ELS
PRNL("Error: ", ~GET-STR-FILE-ERROR )
CEND
END```

And this is fast!

If you want to print the original dates, just add the line "Swap Day By Month(1,2)" before printing the result. In this case, the results are printed with the dates changed.

Output:
```27/8/1883    Krakatoa            8.8
18/5/1980    MountStHelens       7.6
25/1/4567    EdgeCase3           6.1
25/1/4567    EdgeCase4           6.1
```

## AppleScript

```on kernighansEarthquakes(magnitudeToBeat)
-- A local "owner" for the long AppleScript lists. Speeds up references to their items and properties.
script o
property individualEntries : {}
property qualifyingEntries : {}
end script

-- Read the text file assuming it's UTF-8 encoded and get a list of the individual entries.
set textFilePath to (path to desktop as text) & "data.txt"
set earthquakeData to (read file textFilePath as «class utf8»)
set o's individualEntries to earthquakeData's paragraphs
-- Get the input magnitude in text form now rather than coercing it during the repeat.
set magnitudeToBeat to magnitudeToBeat as text

-- Check the entries with AppleScript's text item delimiters set to likely white space characters and considering numeric strings.
-- With these delimiters, the entries' magnitudes will be the last 'text item' in each line
-- (assuming for this exercise that there'll never be white space at the end of any of the lines).
-- Store entries with qualifying magnitudes in a new list.
set astid to AppleScript's text item delimiters
set AppleScript's text item delimiters to {space, tab, character id 160} -- White space characters.
considering numeric strings -- Compare numbers in strings numerically instead of lexically.
repeat with i from 1 to (count o's individualEntries)
set thisEntry to item i of o's individualEntries
if (thisEntry's last text item > magnitudeToBeat) then set end of o's qualifyingEntries to thisEntry
end repeat
end considering

-- Coerce the list of qualifying earthquakes to a single, linefeed-delimited text and return the result.
set AppleScript's text item delimiters to linefeed
set largeEarthquakes to o's qualifyingEntries as text
set AppleScript's text item delimiters to astid

return largeEarthquakes
end kernighansEarthquakes

kernighansEarthquakes(6)
```

### Functional

Checking that the file exists, and discarding any blank lines, while emphasising code reuse, and speed of writing and refactoring:

```use AppleScript version "2.4"
use framework "Foundation"

property magnitude : 6.0
property fp : "~/Desktop/data.txt"

-------------------------- TEST ---------------------------
on run

either(identity, identity, ¬
report(fp, magnitude)))

end run

-------------------- EARTHQUAKE REPORT --------------------

-- report :: FilePath -> Float -> String -> String
on report(fp, threshold)
script
on |λ|(s)
|Right|(unlines({("Magnitudes above " & magnitude as string) & ¬
" in " & fp & ":", ""} & ¬
concatMap(aboveThreshold(threshold), paragraphs of s)))
end |λ|
end script
end report

-- aboveThreshold :: Float -> String -> Bool
on aboveThreshold(threshold)
script
on |λ|(s)
if "" ≠ s and threshold < (item -1 of words of s) as number then
{s}
else
{}
end if
end |λ|
end script
end aboveThreshold

-------------------- REUSABLE GENERICS --------------------

-- Left :: a -> Either a b
on |Left|(x)
{type:"Either", |Left|:x, |Right|:missing value}
end |Left|

-- Right :: b -> Either a b
on |Right|(x)
{type:"Either", |Left|:missing value, |Right|:x}
end |Right|

-- bindLR (>>=) :: Either a -> (a -> Either b) -> Either b
on bindLR(m, mf)
if missing value is not |Left| of m then
m
else
mReturn(mf)'s |λ|(|Right| of m)
end if
end bindLR

-- concatMap :: (a -> [b]) -> [a] -> [b]
on concatMap(f, xs)
set lng to length of xs
set acc to {}
tell mReturn(f)
repeat with i from 1 to lng
set acc to acc & (|λ|(item i of xs, i, xs))
end repeat
end tell
return acc
end concatMap

-- either :: (a -> c) -> (b -> c) -> Either a b -> c
on either(lf, rf, e)
if missing value is |Left| of e then
tell mReturn(rf) to |λ|(|Right| of e)
else
tell mReturn(lf) to |λ|(|Left| of e)
end if
end either

-- identity :: a -> a
on identity(x)
-- The argument unchanged.
x
end identity

-- mReturn :: First-class m => (a -> b) -> m (a -> b)
on mReturn(f)
-- 2nd class handler function lifted into 1st class script wrapper.
if script is class of f then
f
else
script
property |λ| : f
end script
end if
end mReturn

-- readFileLR :: FilePath -> Either String IO String
set ca to current application
set e to reference
set {s, e} to (ca's NSString's ¬
stringWithContentsOfFile:((ca's NSString's ¬
stringWithString:strPath)'s ¬
stringByStandardizingPath) ¬
encoding:(ca's NSUTF8StringEncoding) |error|:(e))
if s is missing value then
|Left|((localizedDescription of e) as string)
else
|Right|(s as string)
end if

-- unlines :: [String] -> String
on unlines(xs)
-- A single string formed by the intercalation
-- of a list of strings with the newline character.
set {dlm, my text item delimiters} to ¬
{my text item delimiters, linefeed}
set str to xs as text
set my text item delimiters to dlm
str
end unlines
```
Output:
```Magnitudes above 6.0 in ~/Desktop/data.txt:

8/27/1883    Krakatoa            8.8
5/18/1980    MountStHelens       7.6```

## APL

Works with: Dyalog APL

This runs from the APL prompt, taking the filename as the right argument and the magnitude as an optional left argument (defaulting to 6).

```quakes←{
⍺←6
nl←⎕UCS 13 10
file←80 ¯1⎕MAP ⍵
lines←((~file∊nl)⊆file)~¨⊂nl
keep←⍺{0::0 ⋄ ⍺ < ⍎3⊃(~⍵∊4↑⎕TC)⊆⍵}¨lines
↑keep/lines
}
```
Output:
```      quakes'data.txt'
8/27/1883    Krakatoa            8.8
5/18/1980    MountStHelens       7.6
5 quakes'data.txt'
8/27/1883    Krakatoa            8.8
5/18/1980    MountStHelens       7.6
3/13/2009    CostaRica           5.1
8 quakes'data.txt'
8/27/1883    Krakatoa            8.8
```

## Arturo

```data: {
3/13/2009    CostaRica           5.1
8/27/1883    Krakatoa            8.8
5/18/1980    MountStHelens       7.6
}

define :earthquake [date place magnitude][]

print first sort.descending.by:'magnitude map split.lines data =>
[to :earthquake split.words &]
```
Output:
`[date:8/27/1883 place:Krakatoa magnitude:8.8]`

## AWK

``` awk '\$3 > 6' data.txt
```

## Bash

```#!/bin/bash
do
[[ \${line##* } =~ ^([7-9]|6\.0*[1-9]).*\$ ]] && echo "\$line"
done < data.txt
```
Output:
```\$ cat data.txt
8/27/1883    Krakatoa            8.8
5/18/1980    MountStHelens       7.6
3/13/2009    CostaRica           5.1
1/23/4567    EdgeCase1           6
1/24/4567    EdgeCase2           6.0
1/25/4567    EdgeCase3           6.1
\$ bash quake.sh
8/27/1883    Krakatoa            8.8
5/18/1980    MountStHelens       7.6
1/25/4567    EdgeCase3           6.1```

## BASIC256

```f = freefile
filename\$ = "data.txt"
open f, filename\$

dim tok\$(1)
while not eof(f)
if (right(tok\$[], 4)) > 6 then print tok\$[]
end while
close f
end```

## C

```#include <stdio.h>
#include <string.h>
#include <stdlib.h>

int main() {
FILE *fp;
char *line = NULL;
size_t len = 0;
char *lw, *lt;
fp = fopen("data.txt", "r");
if (fp == NULL) {
printf("Unable to open file\n");
exit(1);
}
printf("Those earthquakes with a magnitude > 6.0 are:\n\n");
while ((read = getline(&line, &len, fp)) != EOF) {
if (read < 2) continue;   /* ignore blank lines */
lw = strrchr(line, ' ');  /* look for last space */
lt = strrchr(line, '\t'); /* look for last tab */
if (!lw && !lt) continue; /* ignore lines with no whitespace */
if (lt > lw) lw = lt;     /* lw points to last space or tab */
if (atof(lw + 1) > 6.0) printf("%s", line);
}
fclose(fp);
if (line) free(line);
return 0;
}
```
Output:

Using the given file:

```Those earthquakes with a magnitude > 6.0 are:

8/27/1883    Krakatoa            8.8
5/18/1980    MountStHelens       7.6
```

## C#

```using System;
using System.IO;
using System.Linq;
using System.Collections.Generic;

public class Program
{
static void Main() {
foreach (var earthquake in LargeEarthquakes("data.txt", 6))
Console.WriteLine(string.Join(" ", earthquake));
}

static IEnumerable<string[]> LargeEarthquakes(string filename, double limit) =>
let parts = line.Split(default(char[]), StringSplitOptions.RemoveEmptyEntries)
where double.Parse(parts[2]) > limit
select parts;

}
```

## C++

```// Randizo was here!
#include <iostream>
#include <fstream>
#include <string>
using namespace std;

int main()
{
ifstream file("../include/earthquake.txt");

int count_quake = 0;
int column = 1;
string value;
double size_quake;
string row = "";

while(file >> value)
{
if(column == 3)
{
size_quake = stod(value);

if(size_quake>6.0)
{
count_quake++;
row += value + "\t";
cout << row << endl;
}

column = 1;
row = "";
}
else
{
column++;
row+=value + "\t";
}
}

cout << "\nNumber of quakes greater than 6 is " << count_quake << endl;

return 0;
}
```

New version:

```// Jolkdarr was also here!
#include <iostream>
#include <iomanip>
#include <fstream>
#include <string>

int main() {
using namespace std;
ifstream file("data.txt");
int count_quake = 0;
string s1, s2;
double rate;
while (!file.eof()) {
file >> s1 >> s2 >> rate;
if (rate > 6.0) {
cout << s1 << setw(20) << s2 << " " << rate << endl;
count_quake++;
}
}

cout << endl << "Number of quakes greater than 6 is " << count_quake << endl;
return 0;
}
```

## Cixl

```use: cx;

'data.txt' `r fopen lines {
let: (time place mag) @@s split ..;
let: (m1 m2) \$mag @. split &int map ..;
\$m1 6 >= \$m2 0 > and {[\$time @@s \$place @@s \$mag] say} if
} for```
Output:
```8/27/1883 Krakatoa 8.8
5/18/1980 MountStHelens 7.6
```

## COBOL

First, with a data file. This adds a fair amount of verbosity to COBOL. For something this one-off, a simpler cut using ACCEPT from standard in is shown.

```*>
*> Kernighan large earthquake problem
*> Tectonics: cobc -xj kernighan-earth-quakes.cob
*>            quakes.txt with the 3 sample lines
*>            ./kernighan-earth-quakes
*>
>>SOURCE FORMAT IS FREE
IDENTIFICATION DIVISION.
PROGRAM-ID. quakes.

ENVIRONMENT DIVISION.
CONFIGURATION SECTION.
REPOSITORY.
FUNCTION ALL INTRINSIC.

INPUT-OUTPUT SECTION.
FILE-CONTROL.
SELECT quake-data
ASSIGN TO command-filename
ORGANIZATION IS LINE SEQUENTIAL
STATUS IS quake-fd-status.

DATA DIVISION.
FILE SECTION.
FD quake-data RECORD VARYING DEPENDING ON line-length.
01 data-line         PICTURE IS X(32768).

WORKING-STORAGE SECTION.
01 quake-fd-status       PICTURE IS XX.
88 ok                 VALUES ARE "00", "01", "02", "03", "04",
"05", "06", "07", "08", "09".
88 no-more            VALUE IS "10".
88 io-error           VALUE IS HIGH-VALUE.

01 line-length           USAGE IS BINARY-LONG.

01 date-time             PICTURE IS X(10).
01 quake                 PICTURE IS X(20).
01 magnitude             PICTURE IS 99V99.

01 command-filename      PICTURE IS X(80).

PROCEDURE DIVISION.
show-big-ones.

ACCEPT command-filename FROM COMMAND-LINE
IF command-filename IS EQUAL TO SPACES THEN
MOVE "data.txt" TO command-filename
END-IF

OPEN INPUT quake-data
PERFORM status-check
IF io-error THEN
GOBACK
END-IF

PERFORM status-check
PERFORM UNTIL no-more OR io-error
UNSTRING data-line DELIMITED BY ALL SPACES
INTO date-time quake magnitude
END-UNSTRING

IF magnitude IS GREATER THAN 6
DISPLAY date-time SPACE quake SPACE magnitude
END-IF

PERFORM status-check
END-PERFORM

CLOSE quake-data
PERFORM status-check
GOBACK.
*>   ****

status-check.
IF NOT ok AND NOT no-more THEN   *> not normal status, bailing
DISPLAY "io error: " quake-fd-status UPON SYSERR
SET io-error TO TRUE
END-IF
EXIT PARAGRAPH.

END PROGRAM quakes.
```
Output:
```prompt\$ cobc -x kernighans-large-earthquakes.cob
prompt\$ ./kernighans-large-earthquakes quakes.txt
8/27/1883  Krakatoa             08.80
5/18/1980  MountStHelens        07.60
prompt\$ cat quakes.txt
8/27/1883    Krakatoa            8.8
5/18/1980    MountStHelens       7.6
3/13/2009    CostaRica           5.1
```

A slighter shorter-version.

```      *>
*> Tectonics: ./kerighan-earth-quakes <quakes.txt
IDENTIFICATION DIVISION.
PROGRAM-ID. quakes.

DATA DIVISION.

WORKING-STORAGE SECTION.
01 data-line             PICTURE IS X(32768).
88 no-more            VALUE IS HIGH-VALUES.

01 date-time             PICTURE IS X(10).
01 quake                 PICTURE IS X(20).
01 magnitude             PICTURE IS 99V99.

PROCEDURE DIVISION.
show-big-ones.

ACCEPT data-line ON EXCEPTION SET no-more TO TRUE END-ACCEPT
PERFORM UNTIL no-more
UNSTRING data-line DELIMITED BY ALL SPACES
INTO date-time quake magnitude
END-UNSTRING

IF magnitude IS GREATER THAN 6
DISPLAY date-time SPACE quake SPACE magnitude
END-IF

ACCEPT data-line ON EXCEPTION SET no-more TO TRUE END-ACCEPT
END-PERFORM

GOBACK.
END PROGRAM quakes.
```

That cut would be used as

`prompt\$ ./kernighans-large-earthquakes <quakes.txt`

## Cowgol

```include "cowgol.coh";
include "file.coh";

# Process a file line by line
interface LineCb(line: [uint8]);
sub ForEachLine(fcb: [FCB], cb: LineCb) is
var buf: uint8[256];
var ptr := &buf[0];

var length := FCBExt(fcb);
while length != 0 loop
var ch := FCBGetChar(fcb);
[ptr] := ch;
ptr := @next ptr;
if ch == '\n' then
[ptr] := 0;
ptr := &buf[0];
cb(&buf[0]);
end if;
length := length - 1;
end loop;
end sub;

# Get magnitude from line
# Cowgol does not support floating point arithmetic, so the integer and
# fractional parts are returned separately
sub magnitude(line: [uint8]): (i: uint8, frac: uint8) is
i := 0;
frac := 0;
var col: uint8 := 1;
var space: uint8 := 0;
# scan ahead to 3rd column
while col < 3 loop
var ch := [line];
line := @next line;
if ch == 0 then break; end if;
if ch <= ' ' then
while ch <= ' ' and ch != 0 loop
ch := [line];
line := @next line;
end loop;
col := col + 1;
end if;
end loop;
if ch == 0 then
return; # no 3rd column
end if;
line := @prev line;

var n: int32;
var pos: [uint8];
# grab integer part
(n, pos) := AToI(line);
if pos == line then
return; # no value
end if;
i := n as uint8;
if [pos] == '.' then
# grab fractional part
(n, pos) := AToI(@next pos);
frac := n as uint8;
end if;
end sub;

# Print any line that has a magnitude > 6
sub PrintIfGt6 implements LineCb is
var i: uint8;
var frac: uint8;
(i, frac) := magnitude(line);
if i > 6 or (i == 6 and frac > 0) then
print(line);
end if;
end sub;

# Open "data.txt" and scan each line
var quakes: FCB;
if FCBOpenIn(&quakes, "data.txt") != 0 then
print("Error!\n");
ExitWithError();
end if;

ForEachLine(&quakes, PrintIfGt6);```
Output:
```\$ cat data.txt
8/27/1883    Krakatoa            8.8
5/18/1980    MountStHelens       7.6
3/13/2009    CostaRica           5.1
1/23/4567    EdgeCase1           6
1/24/4567    EdgeCase2           6.0
1/25/4567    EdgeCase3           6.1
\$ ./quakes.386
8/27/1883    Krakatoa            8.8
5/18/1980    MountStHelens       7.6
1/25/4567    EdgeCase3           6.1```

## Delphi

Works with: Delphi version 6.0

This code takes advantage of the standard Delphi "TStringGrid" object to do most of the heavy lifting. It is initially used to read the earthquake file into memory, breaking it up into of individual lines as it goes. Then the individual fields are stored in structurs/records attached to the data. finally, the data is sorted by magnitude so the earthquakes of magnitudes greater than six can be extracted. Because the data is now neatly organized in memory, all kinds of other process could be done, including sorting it by date or location. To make the problem more realistic, I extracted actual earthquake data from the first few months of 2023. I've post the data for other people to test here: EarthQuakes.txt

```{Structure used to contain all the earthquake data}

type TQuakeInfo = record
Date: TDate;
Name: string;
Mag: double;
end;
type PQuakeInfo = ^TQuakeInfo;

{Used to contain individual fields of the earthquake data}

type TStringArray = array of string;

function SortCompare(List: TStringList; Index1, Index2: Integer): Integer;
{Custom sort routine to sort data by magnitude }
var QI1,QI2: TQuakeInfo;
begin
QI1:=PQuakeInfo(List.Objects[Index1])^;
QI2:=PQuakeInfo(List.Objects[Index2])^;
Result:=Round(QI2.Mag*10)-Round(QI1.Mag*10);
end;

procedure GetFields(S: string; var SA: TStringArray);
{Extract the three fields from each row of data}
var I,F: integer;
begin
SetLength(SA,3);
for I:=0 to High(SA) do SA[I]:='';
F:=0;
for I:=1 to Length(S) do
if S[I] in [#\$09,#\$20] then Inc(F)
else SA[F]:=SA[F]+S[I];
end;

procedure AnalyzeEarthQuakes(Filename: string; Memo: TMemo);
{Read earhtquake data from specified file}
{Extract the individual fields and sort and display it}
var SL: TStringList;
var I: integer;
var S: string;
var FA: TStringArray;
var QI: PQuakeInfo;
begin
SL:=TStringList.Create;
try
{Read file, separating it into rows}
{Process each row}
for I:=0 to SL.Count-1 do
begin
S:=SL[I];
{Separate row into fields}
GetFields(S,FA);
{Store data as objects in TStringList}
New(QI);
QI.Date:=StrToDate(FA[0]);
QI.Name:=FA[1];
QI.Mag:=StrToFloat(FA[2]);
SL.Objects[I]:=TObject(QI);
end;
{Sort data by magnitude}
SL.CustomSort(SortCompare);
{Display sorted data}
for I:=0 to SL.Count-1 do
begin
if PQuakeInfo(SL.Objects[I]).Mag<6 then break;
S:=FormatDateTime('dd/mm/yyyy', PQuakeInfo(SL.Objects[I]).Date);
S:=S+Format('  %-34s',[PQuakeInfo(SL.Objects[I]).Name]);
S:=S+Format('  %5f',[PQuakeInfo(SL.Objects[I]).Mag]);
end;
{Dispose of memory}
finally
for I:=0 to SL.Count-1 do Dispose(PQuakeInfo(SL.Objects[I]));
SL.Free;
end;
end;

procedure ShowEarthQuakes(Memo: TMemo);
begin
AnalyzeEarthQuakes('EarthQuakes.txt',Memo);
end;
```
Output:
```06/02/2023  Turkey_Kahramanmaras                 7.80
09/01/2023  Indonesia_Maluku                     7.60
06/02/2023  Turkey_Kahramanmaras                 7.50
02/04/2023  Papua_New_Guinea_East_Sepik          7.00
18/01/2023  Indonesia_North_Maluku               7.00
14/04/2023  Indonesia_East_Java                  7.00
08/01/2023  Vanuatu_Sanma                        7.00
20/01/2023  Argentina_Santiago_del_Estero        6.80
18/04/2023  South_of_theFiji_Islands             6.70
06/02/2023  Turkey_Gaziantep                     6.70
01/03/2023  Papua_New_Guinea_West_New_Britain    6.60
02/03/2023  Vanuatu_Sanma                        6.50
03/04/2023  Russia_Kamchatka_Krai                6.50
22/03/2023  Argentina_Jujuy                      6.50
24/01/2023  Argentina_Santiago_del_Estero        6.40
19/04/2023  Papua_New_Guinea_West_New_Britain    6.30
16/01/2023  Japan_Bonin_Islands                  6.30
20/02/2023  Turkey_Hatay                         6.30
23/02/2023  Indonesia_North_Maluku               6.30
21/04/2023  Indonesia_Southeast_Sulawesi         6.30
30/03/2023  Chile_Maule                          6.30
04/04/2023  Panama_Chiriqu-                      6.30
25/02/2023  Papua_New_Guinea_West_New_Britain    6.20
04/04/2023  Philippines_Bicol                    6.20
27/03/2023  Solomon_Islands_Isabel               6.10
03/04/2023  Indonesia_North_Sumatra              6.10
17/02/2023  Indonesia_Maluku                     6.10
15/02/2023  Philippines_Bicol                    6.10
15/01/2023  Indonesia_Aceh                       6.10
28/03/2023  Japan_Hokkaido                       6.00
18/01/2023  Indonesia_Gorontalo                  6.00
01/02/2023  Philippines_Davao                    6.00
06/02/2023  Turkey_Kahramanmaras                 6.00
06/02/2023  Turkey_Malatya                       6.00
25/02/2023  Japan_Hokkaido                       6.00
```

## D

Translation of: Kotlin
```import std.conv : to;
import std.regex : ctRegex, split;
import std.stdio : File, writeln;

void main() {
auto ctr = ctRegex!"\\s+";

writeln("Those earthquakes with a magnitude > 6.0 are:");
foreach (line; File("data.txt").byLineCopy) {
auto parts = split(line, ctr);
if (parts[2].to!double > 6.0) {
writeln(line);
}
}
}
```
Output:
```Those earthquakes with a magnitude > 6.0 are:
8/27/1883    Krakatoa            8.8
5/18/1980    MountStHelens       7.6```

## Emacs Lisp

```(with-temp-buffer
(insert-file-contents "data.txt")
(goto-char (point-min))
(while (not (eobp))
(let* ((line (buffer-substring (line-beginning-position)
(line-end-position)))
(magn (nth 2 (split-string line "\\s-+"))))
(when (> (string-to-number magn) 6.0)
(message line)))
(forward-line 1)))
```

## Factor

`lines` is a convenience word that reads lines from standard input. If you don't want to type them all in yourself, it is suggested that you give the program a file to read. For example, on the Windows command line: `factor kernighan.factor < earthquakes.txt`

```USING: io math math.parser prettyprint sequences splitting ;
IN: rosetta-code.kernighan

lines [ "\s" split last string>number 6 > ] filter .
```

## FreeBASIC

```Dim As Long f
f = Freefile
Dim As String nomArchivo = "data.txt"

If Open(nomArchivo For Input As #f)  Then
Print "ERROR: No se pudo abrir " ; nomArchivo
Sleep : End
End If

Dim As String tok(), lin
Do While Not Eof(f)
Line Input #f, lin
If Val(Right(lin, 3)) > 6 Then Print lin
Loop
Close #f
Sleep```

## Go

```package main

import (
"bufio"
"fmt"
"os"
"strconv"
"strings"
)

func main() {
f, err := os.Open("data.txt")
if err != nil {
fmt.Println("Unable to open the file")
return
}
defer f.Close()
fmt.Println("Those earthquakes with a magnitude > 6.0 are:\n")
input := bufio.NewScanner(f)
for input.Scan() {
line := input.Text()
fields := strings.Fields(line)
mag, err := strconv.ParseFloat(fields[2], 64)
if err != nil {
fmt.Println("Unable to parse magnitude of an earthquake")
return
}
if mag > 6.0 {
fmt.Println(line)
}
}
}
```
Output:
```Those earthquakes with a magnitude > 6.0 are:

8/27/1883    Krakatoa            8.8
5/18/1980    MountStHelens       7.6
```

## Groovy

Translation of: Kotlin
```import java.util.regex.Pattern

class LargeEarthquake {
static void main(String[] args) {
def r = Pattern.compile("\\s+")
println("Those earthquakes with a magnitude > 6.0 are:\n")
def f = new File("data.txt")
f.eachLine { it ->
if (r.split(it)[2].toDouble() > 6.0) {
println(it)
}
}
}
}
```
Output:
```Those earthquakes with a magnitude > 6.0 are:

8/27/1883    Krakatoa            8.8
5/18/1980    MountStHelens       7.6```

```import qualified Data.ByteString.Lazy.Char8 as C

main :: IO ()
main = do
mapM_ print \$
C.lines cs >>=
(\x ->
[ x
| 6 < (read (last (C.unpack <\$> C.words x)) :: Float) ])
```
Output:
```"8/27/1883    Krakatoa            8.8"
"5/18/1980    MountStHelens       7.6"```

## J

```NB. this program is designed for systems where the line ending is either LF or CRLF

NB. filename select_magnitude minimum
NB. default file is /tmp/famous.quakers

select_magnitude=: '/tmp/famous.quakers'&\$: : (4 :0)
data =. 1!:1 boxopen x       NB. read the file
data =. data -. CR           NB. remove nasty carriage returns
data =. ,&LF^:(LF~:{:) data  NB. append new line if none found
lines =. [;._2 data          NB. split the literal based on the final character
magnitudes =. ". _1&{::@(<;._2)@(,&' ')@deb"1 lines
(y <: magnitudes) # lines
)
```
```   select_magnitude 6
8/27/1883    Krakatoa            8.8
5/18/1980    MountStHelens       7.6
```

## Java

Input file contains sample data shown in the task

```import java.io.BufferedReader;

public class KernighansLargeEarthquakeProblem {

public static void main(String[] args) throws Exception {
String inLine = null;
String[] split = inLine.split("\\s+");
double magnitude = Double.parseDouble(split[2]);
if ( magnitude > 6 ) {
System.out.println(inLine);
}
}
}

}

}
```
Output:
```8/27/1883    Krakatoa            8.8
5/18/1980    MountStHelens       7.6
```

## JavaScript

Input file contains sample data shown in the task. The code below uses Nodejs to read the file.

```const fs = require("fs");

const args = process.argv.slice(2);
if (!args.length) {
console.error("must supply file name");
process.exit(1);
}

const fname = args[0];

console: false,
});

const fields = line.split(/\s+/);
if (+fields[fields.length - 1] > 6) {
console.log(line);
}
});
```
Output:
```8/27/1883    Krakatoa            8.8
5/18/1980    MountStHelens       7.6
```

## jq

Works with: jq

Works with gojq, the Go implementation of jq

To meet the task requirements in a minimal way, one could invoke jq as follows:

```jq -Rrn 'inputs | . as \$line | [splits("  *") ] | select((.[2]|tonumber) > 6) | \$line' data.txt
```

The program shown in the following subsection, by contrast, determines the file name dynamically and includes some error-checking. The output shown below is based on the invocation:

```jq -Rrn -f large-earthquake-problem.jq data.txt
```

where data.txt is as for Snobol.

```input as \$one
| "The earthquakes from \(input_filename) with a magnitude greater than 6 are:\n",
( \$one, inputs
| . as \$line
| [splits("  *")]
| if length < 3
then "WARNING: invalid line:\n\(\$line)"
else try ((.[2] | tonumber) as \$mag
| select(\$mag > 6)
| \$line) catch "WARNING: column 3 is not a recognized number in the line:\n\(\$line)"
end )```
Output:
```The earthquakes from data.txt with a magnitude greater than 6 are:

8/27/1883    Krakatoa            8.8
5/18/1980    MountStHelens       7.6
1/25/4567    EdgeCase3           6.1
```

## Julia

Using the example data as a small text file.

```using DataFrames, CSV

df = CSV.File("kernighansproblem.txt", delim=" ", ignorerepeated=true,
header=["Date", "Location", "Magnitude"], types=[DateTime, String, Float64],
dateformat="mm/dd/yyyy") |> DataFrame

println(filter(row -> row[:Magnitude] > 6, df))
```
Output:
```
2×3 DataFrame
│ Row │ Date                │ Location      │ Magnitude │
│     │ DateTime            │ String        │ Float64   │
├─────┼─────────────────────┼───────────────┼───────────┤
│ 1   │ 1883-08-27T00:00:00 │ Krakatoa      │ 8.8       │
│ 2   │ 1980-05-18T00:00:00 │ MountStHelens │ 7.6       │

```

## Klingphix

```arg pop nip len dup

( [get nip]
[drop drop "data.txt"]
) if

%f
dup "r" fopen !f
\$f 0 < ( [drop "Could not open '" print print "' for reading" print -1 end ] [drop] ) if

[dup split 3 get tonum 6 > ( [drop print nl] [drop drop] ) if]
[\$f fgets dup -1 #]
while

drop
\$f fclose

"End " input```

## Kotlin

```// Version 1.2.40

import java.io.File

fun main(args: Array<String>) {
val r = Regex("""\s+""")
println("Those earthquakes with a magnitude > 6.0 are:\n")
File("data.txt").forEachLine {
if (it.split(r)[2].toDouble() > 6.0) println(it)
}
}
```
Output:

Using the given file:

```Those earthquakes with a magnitude > 6.0 are:

8/27/1883    Krakatoa            8.8
5/18/1980    MountStHelens       7.6
```

## Lua

For each line, the Lua pattern "%S+\$" is used to capture between the final space character and the end of the line.

```-- arg[1] is the first argument provided at the command line
for line in io.lines(arg[1] or "data.txt") do  -- use data.txt if arg[1] is nil
magnitude = line:match("%S+\$")
if tonumber(magnitude) > 6 then print(line) end
end
```

## M2000 Interpreter

```Module Find_Magnitude  {
data\$={8/27/1883    Krakatoa            8.8
5/18/1980    MountStHelens       7.6
3/13/2009    CostaRica           5.1
1/23/4567    EdgeCase1           6
1/24/4567    EdgeCase2           6.0
1/25/4567    EdgeCase3           6.1
}
Open "data.txt" for output as F
Print #F, data\$;
Close #F
Open "data.txt" for input as F
While not eof(#F)
Line Input #f, part\$
REM if val(mid\$(part\$,30))>6 then print part\$
if val(mid\$(part\$,rinstr(rtrim\$(part\$)," ")))>6 then print part\$
End While
Close #F
}
Find_Magnitude```

Output:
```8/27/1883    Krakatoa            8.8
5/18/1980    MountStHelens       7.6
1/25/4567    EdgeCase3           6.1
```

## Mathematica / Wolfram Language

```Import["data.txt", "Table"] // Select[Last /* GreaterThan[6]]
```

## Nim

Here is one way to do that:

```import strscans

for line in "data.txt".lines:
var date, name: string
var magnitude: float
if scanf(line, "\$+ \$s\$+ \$s\$f", date, name, magnitude):
if magnitude > 6:
echo line
# else wrong line: ignore.
```

Here is another way with less checks:

```import strutils

for line in "data.txt".lines:
let magnitude = line.rsplit(' ', 1)[1]
if magnitude.parseFloat() > 6:
echo line
```
Output:
```8/27/1883    Krakatoa            8.8
5/18/1980    MountStHelens       7.6```

## Perl

```perl -n -e '/(\S+)\s*\$/ and \$1 > 6 and print' data.txt
```

## Phix

```with javascript_semantics
constant filename = "data.txt"
string text = iff(platform()=JS or not file_exists(filename)?"""
8/27/1883    Krakatoa            8.8
5/18/1980    MountStHelens       7.6
3/13/2009    CostaRica           5.1""" : get_text(filename))
sequence lines = split_any(text,"\r\n")
for i=1 to length(lines) do
sequence r = scanf(lines[i],"%s %f")
if length(r)=1 and r[1][2]>6 then
printf(1,"%s\n",{lines[i]})
end if
end for
```
Output:
```"8/27/1883    Krakatoa            8.8"
"5/18/1980    MountStHelens       7.6"
```

## Phixmonti

```argument tail nip len dup
if
get nip
else
drop drop "data.txt"
endif

dup "r" fopen
dup 0 < if drop "Could not open '" print print "' for reading" print -1 quit endif
nip

true
while
dup fgets
dup 0 < if
drop false
else
dup split 3 get tonum 6 > if drop print else drop drop endif
true
endif
endwhile
fclose```

## PHP

Parse using PHP's fscanf().

```<?php

// make sure filename was specified on command line
if ( ! isset( \$argv[1] ) )
die( 'Data file name required' );

// open file and check for success
if ( ! \$fh = fopen( \$argv[1], 'r' ) )
die ( 'Cannot open file: ' . \$argv[1] );

while ( list( \$date, \$loc, \$mag ) = fscanf( \$fh, "%s %s %f" ) ) {
if ( \$mag > 6 ) {
printf( "% -12s % -19s %.1f\n", \$date, \$loc, \$mag );
}
}

fclose( \$fh );
```

Usage: Specify file name on command line. Ex: `php eq.php data.txt`

Output:
```8/27/1883    Krakatoa            8.8
5/18/1980    MountStHelens       7.6
```

## PicoLisp

```(load "@lib/misc.l")

(in "kernighan.txt"
(until (eof)
(when (> Mag 6)
(prinl (align -10 Date) " " (align -15 Quake) " " Mag)))))
(bye)```
Output:
```\$ ./kernighan.l
8/27/1883  Krakatoa        9
5/18/1980  MountStHelens   8
```

## Prolog

Works with: SWI Prolog

Example command line: `swipl kernighans_earthquake.pl earthquake.txt`.

```:- initialization(main, main).

process_line(Line):-
split_string(Line, "\s\t", "\s\t", [_, _, Magnitude_string]),
Magnitude > 6,
!,
writef('%w\n', [Line]).
process_line(_).

process_stream(Stream):-
String \= end_of_file,
!,
process_line(String),
process_stream(Stream).
process_stream(_).

process_file(File):-
process_stream(Stream),
close(Stream).

main([File]):-
process_file(File),
!.
main(_):-
swritef(Message, 'File argument is missing\n', []),
write(user_error, Message).
```
Output:
```8/27/1883    Krakatoa            8.8
5/18/1980    MountStHelens       7.6
```

## PureBasic

```If OpenConsole() And ReadFile(0,"data.txt")
PrintN("Those earthquakes with a magnitude > 6.0 are:")
While Not Eof(0)
If ValF((StringField(buf\$,CountString(buf\$," ")+1," ")))>6.0
PrintN(buf\$)
EndIf
Wend
CloseFile(0)
Input()
EndIf```
Output:
```Those earthquakes with a magnitude > 6.0 are:
8/27/1883    Krakatoa            8.8
5/18/1980    MountStHelens       7.6```

## Python

Typed into a bash shell or similar:

```python -c '
with open("data.txt") as f:
for ln in f:
if float(ln.strip().split()[2]) > 6:
print(ln.strip())'
```

Or, if scale permits a file slurp and a parse retained for further processing, we can combine the parse and filter with a concatMap abstraction:

```from os.path import expanduser
from functools import (reduce)
from itertools import (chain)

# largeQuakes :: Int -> [String] -> [(String, String, String)]
def largeQuakes(n):
def quake(threshold):
def go(x):
ws = x.split()
return [tuple(ws)] if threshold < float(ws[2]) else []
return lambda x: go(x)
return concatMap(quake(n))

# main :: IO ()
def main():
print (
largeQuakes(6)(
)
)

# GENERIC ABSTRACTION -------------------------------------

# concatMap :: (a -> [b]) -> [a] -> [b]
def concatMap(f):
return lambda xs: list(
chain.from_iterable(
map(f, xs)
)
)

# MAIN ---
if __name__ == '__main__':
main()
```
Output:
`[('8/27/1883', 'Krakatoa', '8.8'), ('5/18/1980', 'MountStHelens', '7.6')]`

## Racket

The file specified contains the three lines from the task description.

This is just a file filter, matching lines are printed out.

```#lang racket

(with-input-from-file "data/large-earthquake.txt"
(λ ()
#:when (> (string->number (third (string-split s))) 6))
(displayln s))))
```

Or, defining a list -> list function in terms of filter:

```#lang racket

; largeQuakes :: Int -> [String] -> [String]
(define (largeQuakes n xs)
(filter
(λ (x)
(< n (string->number (last (string-split x)))))
xs))

; main :: IO ()
(module* main #f
(display
(unlines
(largeQuakes
6

; GENERIC ---------------------------------------------

; lines :: String -> [String]
(define (lines s)
(string-split s "\n"))

; readFile :: FilePath -> IO String
(file->string
(expand-user-path fp)))

; unlines :: [String] -> String
(define (unlines xs)
(string-join xs "\n"))
```
Output:
```8/27/1883    Krakatoa            8.8
5/18/1980    MountStHelens       7.6```

To combine filtering with more pre-processing, we can use concatMap in place of filter:

```#lang racket

(require gregor) ; Date parsing

; test :: IO ()
(module* main #f
(for
([q ((quakesAbove 6)
(writeln q)))

; quakesAbove :: Int -> [String] -> [(Date, String, Float)]
(define (quakesAbove n)
(λ (xs)
((concatMap
(λ (x)
(local [(define-values (dte k mgn)
(apply values (string-split x)))
(define m (string->number mgn))]
(if (< n m)
(list (list (parse-date dte "M/d/y") k m))
'()))))
xs)))

; GENERIC ---------------------------------------------

; concatMap :: (a -> [b]) -> [a] -> [b]
(define (concatMap f)
(λ (xs)
(foldr (λ (x a) (append (f x) a)) '() xs)))

; lines :: String -> [String]
(define (lines s)
(string-split s "\n"))

; readFile :: FilePath -> IO String
(file->string
(expand-user-path fp)))
```
Output:
```(#<date 1883-08-27> "Krakatoa" 8.8)
(#<date 1980-05-18> "MountStHelens" 7.6)```

## Raku

(formerly Perl 6)

Works with: Rakudo version 2018.03

Pass in a file name, or use default for demonstration purposes.

```\$_ = @*ARGS[0] ?? @*ARGS[0].IO !! q:to/END/;
8/27/1883    Krakatoa            8.8
5/18/1980    MountStHelens       7.6
3/13/2009    CostaRica           5.1
END

map { .say if .words[2] > 6 }, .lines;
```

## REXX

A little extra coding was added to provide:

•   an output title   (with centering and better alignment)
•   an error message for when the input file wasn't found   (or is empty)
•   the number of records read
•   the number of records that met the qualifying magnitude
•   the qualifying magnitude
```/*REXX program to read a file containing a list of earthquakes:   date, site, magnitude.*/
parse arg iFID mMag .                            /*obtain optional arguments from the CL*/
if iFID=='' | iFID==","  then iFID= 'earthquakes.dat' /*Not specified?  Then use default*/
if mMag=='' | mMag==","  then mMag= 6                 /* "      "         "   "     "   */
#=0                                              /*# of earthquakes that meet criteria. */
do j=0  while lines(iFID)\==0                 /*read all lines in the input file.    */
if j==0  then say 'Reading from file: ' iFID  /*show the name of the file being read.*/
parse value linein(iFID) with date site mag . /*parse three words from an input line.*/
if mag<=mMag  then iterate                    /*Is the quake too small?  Then skip it*/
#= # + 1;     if j==0  then say               /*bump the number of qualifying quakes.*/
if #==1  then say center('date', 20, "═")     '=magnitude='     center("site", 20, '═')
say               center(date, 20)      center(mag/1, 11)   '  '        site
end   /*j*/                                   /*stick a fork in it,  we're all done. */
say
say
if j\==0  then say j  'records read from file: ' iFID
say
if j==0  then say er 'file    '          iFID           "   is empty or not found."
else say #  ' earthquakes listed whose magnitude is  ≥ ' mMag
```
output   when using the default inputs:
```Reading from file:  earthquakes.dat

════════date════════ =magnitude= ════════site════════
08/27/1883          8.8        Krakatoa
05/18/1980          7.6        MountStHelens

3 records read from file:  earthquakes.dat

2  earthquakes listed whose magnitude is  ≥  6
```

## Ring

```# Project  : Kernighans large earthquake problem

nr = 0
equake = list(3)
fn = "equake.txt"
fp = fopen(fn,"r")

while not feof(fp)
nr = nr + 1
end
fclose(fp)
for n = 1 to len(equake)
for m = 1 to len(equake[n])
if equake[n][m] = " "
sp = m
ok
next
sptemp = right(equake[n],len(equake[n])-sp)
sptemo = number(sptemp)
if sptemp > 6
see equake[n] + nl
ok
next```

Output:

```8/27/1883    Krakatoa            8.8
5/18/1980    MountStHelens   7.6
```

## Ruby

```ruby -nae "\$F[2].to_f > 6 && print" data.txt
```

A more interesting problem. Print only the events whose magnitude is above average.

Contents of the file:

```8/27/1883    Krakatoa            8.8
5/18/1980    MountStHelens       7.6
3/13/2009    CostaRica           5.1
2000-02-02  Foo               7.7
1959-08-08   Bar             6.2
1849-09-09  Pym                9.0
```

The command:

```ruby -e"m=\$<.to_a;f=->s{s.split[2].to_f};a=m.reduce(0){|t,s|t+f[s]}/m.size;puts m.select{|s|f[s]>a}" e.txt
```

Output:

```8/27/1883    Krakatoa            8.8
5/18/1980    MountStHelens       7.6
2000-02-02  Foo               7.7
1849-09-09  Pym                9.0
```

## Rust

```fn main() -> Result<(), Box<dyn std::error::Error>> {

let line = line?;

let magnitude = line
.split_whitespace()
.nth(2)
.and_then(|it| it.parse::<f32>().ok())
.ok_or_else(|| format!("Could not parse scale: {}", line))?;

if magnitude > 6.0 {
println!("{}", line);
}
}

Ok(())
}
```

## Scala

```scala.io.Source.fromFile("data.txt").getLines
.map("\\s+".r.split(_))
.filter(_(2).toDouble > 6.0)
.map(_.mkString("\t"))
.foreach(println)
```

## Snobol

This is hard-coded to read the input from "data.txt".

```        input(.quake, 1,, 'data.txt')       :f(err)
num = '.0123456789'

line    test = quake                        :f(end)
test span(num) . magnitude rpos(0)  :f(line)
output = gt(magnitude,6) test       :(line)

err     output = 'Error!'
end
```
Output:
```\$ cat data.txt
8/27/1883    Krakatoa            8.8
5/18/1980    MountStHelens       7.6
3/13/2009    CostaRica           5.1
1/23/4567    EdgeCase1           6
1/24/4567    EdgeCase2           6.0
1/25/4567    EdgeCase3           6.1
\$ snobol4 quakes.sno
8/27/1883    Krakatoa            8.8
5/18/1980    MountStHelens       7.6
1/25/4567    EdgeCase3           6.1```

## Swift

Expects the program to be started with the path to the data file.

```import Foundation

guard let path = Array(CommandLine.arguments.dropFirst()).first else {
fatalError()
}

let fileData = FileManager.default.contents(atPath: path)!
let eventData = String(data: fileData, encoding: .utf8)!

for line in eventData.components(separatedBy: "\n") {
guard let lastSpace = line.lastIndex(of: " "), // Get index of last space
line.index(after: lastSpace) != line.endIndex, // make sure the last space isn't the end of the line
let magnitude = Double(String(line[line.index(after: lastSpace)])),
magnitude > 6 else { // Finally check the magnitude
continue
}

print(line)
}
```

## Tcl

Inspired by awk.

```catch {console show}          ;## show console when running from tclwish
catch {wm withdraw .}

set filename "data.txt"
set fh [open \$filename]
set NR 0                ;# number-of-record, means linenumber

while {[gets \$fh line]>=0} {        ;# gets returns length of line, -1 means eof
incr NR
set  line2 [regexp -all -inline {\S+} \$line]  ;# reduce multiple whitespace
set  fld   [split \$line2]   ;# split line into fields, at whitespace
set  f3    [lindex \$fld 2]  ;# zero-based
#set  NF    [llength \$fld]       ;# number-of-fields

if {\$f3 > 6} { puts "\$line" }
}
close \$fh
```

## Visual Basic .NET

Translation of: C#
```Imports System.IO

Module Module1

Function LargeEarthquakes(filename As String, limit As Double) As IEnumerable(Of String())
Let parts = line.Split(CType(Nothing, Char()), StringSplitOptions.RemoveEmptyEntries)
Where Double.Parse(parts(2)) > limit
Select parts
End Function

Sub Main()
For Each earthquake In LargeEarthquakes("data.txt", 6)
Console.WriteLine(String.Join(" ", earthquake))
Next
End Sub

End Module
```

## V (Vlang)

```import os
fn main() {
println('Those earthquakes with a magnitude > 6.0 are:\n')
for line in lines {
fields := line.fields()
mag := fields[2].f64()
if mag > 6.0 {
println(line)
}
}
}```
Output:
```Those earthquakes with a magnitude > 6.0 are:

8/27/1883    Krakatoa            8.8
5/18/1980    MountStHelens       7.6
```

## Wren

Library: Wren-pattern
```import "io" for File
import "os" for Process
import "./pattern" for Pattern

var args = Process.arguments
if (args.count != 1) Fiber.abort("Please pass just the name of the date file.")
var fileName = args[0]
var lines = File.read(fileName).split("\n").map { |l| l.trim() }.where { |l| l != "" }
var p = Pattern.new("+1/s")
System.print("The earthquakes from '%(fileName)' with a magnitude of greater than 6 are:\n")
for (line in lines) {
var data = p.splitAll(line)
if (data.count != 3) Fiber.abort("Invalid line : %(line)")
var mag = Num.fromString(data[2])
if (mag > 6) System.print(line)
}
```
Output:
```The earthquakes from 'data.txt' with a magnitude of greater than 6 are:

8/27/1883    Krakatoa            8.8
5/18/1980    MountStHelens       7.6
```

## XPL0

Usage: quake <data.txt

```int C;
[loop   [OpenO(8);              \get line from input file
repeat  C:= ChIn(1);
ChOut(8, C);    \save it in buffer device 8
if C = \$1A\EOF\ then quit;
until   C = \$0A\LF\;
OpenI(8);
repeat until ChIn(8) <= \$20\space\;
repeat until ChIn(8) >  \$20\space\;
repeat until ChIn(8) <= \$20\space\;
if RlIn(8) > 6.0 then
[OpenI(8);          \output saved line to console
repeat  C:= ChIn(8);
ChOut(0, C);
until   C = \$0A\LF\;
];
];
]```
Output:
```8/27/1883    Krakatoa            8.8
5/18/1980    MountStHelens       7.6
1/25/4567    EdgeCase3           6.1

for data.txt
8/27/1883    Krakatoa            8.8
5/18/1980    MountStHelens       7.6
3/13/2009    CostaRica           5.1
1/23/4567    EdgeCase1           6
1/24/4567    EdgeCase2           6.0
1/25/4567    EdgeCase3           6.1
```

## Yabasic

```if peek("argument") then
filename\$ = peek\$("argument")
else
filename\$ = "data.txt"
end if

dim tok\$(1)
a = open(filename\$)
if not a error "Could not open '" + filename\$ + "' for reading"
while(not eof(a))
line input #a a\$
void = token(a\$, tok\$())
if val(tok\$(3)) > 6 print a\$
wend
close a```

## zkl

While lexical comparsions [of numeric data] are fine for this problem, it is bad practice so I don't do it (written so text is automatically converted to float).

```fcn equake(data,out=Console){
data.pump(out,fcn(line){ 6.0line.split()[-1] },Void.Filter)
}```
```equake(Data(Void,
#<<<
"8/27/1883    Krakatoa            8.8\n"
"5/18/1980    MountStHelens       7.6\n"
"3/13/2009    CostaRica           5.1\n"
#<<<
));```

or

`equake(File("equake.txt"));`

or

`\$ zkl --eval 'File.stdin.pump(Console,fcn(line){ 6.0<line.split()[-1] },Void.Filter)' < equake.txt`
Output:
```8/27/1883    Krakatoa            8.8
5/18/1980    MountStHelens       7.6
```