Shift list elements to left by 3

Shift list elements to left by 3 is a draft programming task. It is not yet considered ready to be promoted as a complete task, for reasons that should be found in its talk page.

Task

Shift list elements to left by   3.

      shift  = [1,2,3,4,5,6,7,8,9]
      result = [4, 5, 6, 7, 8, 9, 1, 2, 3]

11l

Translation of: Python

F rotate(l, n)
   V k = (l.len + n) % l.len
   R l[k ..] [+] l[0 .< k]

V l = [1, 2, 3, 4, 5, 6, 7, 8, 9]
print(l‘  =>  ’rotate(l, 3))

Output:

[1, 2, 3, 4, 5, 6, 7, 8, 9]  =>  [4, 5, 6, 7, 8, 9, 1, 2, 3]

Action!

PROC PrintArray(INT ARRAY a INT size)
  INT i

  Put('[)
  FOR i=0 TO size-1
  DO
    IF i>0 THEN Put(' ) FI
    PrintI(a(i))
  OD
  Put(']) PutE()
RETURN

PROC ShiftLeft(INT ARRAY a INT size)
  INT i,j,tmp

  tmp=a(0)
  FOR i=0 TO size-2
  DO
    a(i)=a(i+1)
  OD
  a(size-1)=tmp
RETURN

PROC ShiftLeftNTimes(INT ARRAY a INT size,times)
  INT i

  FOR i=1 TO times
  DO
    ShiftLeft(a,size)
  OD
RETURN

PROC Test(INT ARRAY a INT size,offset)
  PrintArray(a,size)
  ShiftLeftNTimes(a,size,3)
  PrintArray(a,size)
RETURN

PROC Main()
  INT ARRAY a=[1 2 3 4 5 6 7 8 9]

  Test(a,9,-3)
RETURN

Output:

Screenshot from Atari 8-bit computer

[1 2 3 4 5 6 7 8 9]
[4 5 6 7 8 9 1 2 3]

Ada

Using slices and array concatenation.

with Ada.Text_Io;

procedure Shift_Left is

   Shift_Count : constant := 3;

   type List_Type is array (Positive range <>) of Integer;

   procedure Put_List (List : List_Type) is
      use Ada.Text_Io;
   begin
      for V of List loop
         Put (V'Image); Put ("  ");
      end loop;
      New_Line;
   end Put_List;

   Shift : List_Type := (1, 2, 3, 4, 5, 6, 7, 8, 9);
begin
   Put_List (Shift);

   Shift :=
     Shift (Shift'First + Shift_Count .. Shift'Last) &
       Shift (Shift'First .. Shift_Count);

   Put_List (Shift);
end Shift_Left;

Output:

 1   2   3   4   5   6   7   8   9
 4   5   6   7   8   9   1   2   3

ALGOL 68

BEGIN
    # shifts in place the elements of a left by n                          #
    PRIO <<:= = 1;
    OP   <<:= = ( REF[]INT a, INT n )REF[]INT:
         BEGIN
            INT    a length = ( UPB a - LWB a ) + 1;
            IF n < a length AND n > 0 THEN
                # the amount to shift is less than the length of the array #
                [ 1 : a length ]INT shifted;
                shifted[ 1                    : a length - n ] := a[ n + 1 :   @ 1 ];
                shifted[ ( a length + 1 ) - n :              ] := a[ 1     : n @ 1 ];
                a[ @ 1 ] := shifted
            FI;
            a
         END # <<:= # ;
    # prints the elements of v                                             #
    OP   PRINT = ( []INT v )VOID:
         BEGIN
            print( ( "[" ) );
            IF LWB v <= UPB v THEN
                print( ( whole( v[ LWB v ], 0 ) ) );
                FOR i FROM LWB v + 1 TO UPB v DO
                    print( ( "," , whole( v[ i ], 0 ) ) )
                OD
            FI;
            print( ( "]" ) )
         END # PRINT # ;            
    [ 1 : 9 ]INT v := ( 1, 2, 3, 4, 5, 6, 7, 8, 9 );
    PRINT v;
    print( ( " -> " ) );
    v <<:= 3;
    PRINT v;
    print( ( newline ) )
END

Output:

[1,2,3,4,5,6,7,8,9] -> [4,5,6,7,8,9,1,2,3]

ALGOL W

Translation of: ALGOL 68

begin
    % increments a and returns the new value %
    integer procedure inc ( integer value result a ) ; begin a := a + 1; a end;
    % shifts in place the elements of a left by n, a must have bounds lb::ub  %
    procedure  rotateLeft ( integer array a ( * ); integer value lb, ub, n ) ;
        if n < ( ub - lb ) and n > 0 then begin
            % the amount to shift is less than the length of the array %
            integer array shifted ( 1 :: n );
            integer aPos;
            for i := 0 until n - 1 do shifted( i ) := a( lb + i );
            for i := lb until ub - n do a( i ) := a( i + n );
            aPos := ub - n;
            for i := 0 until n - 1 do a( inc( aPos ) ) := shifted( i );
        end rotateLeft ;
    % prints the elements of v from lb to ub %
    procedure printArray ( integer array v ( * ); integer value lb, ub ) ;
    begin
        writeon( s_w := 0, "[" );
        if lb <= ub then begin
            writeon( i_w := 1, s_w := 0, v( lb ) );
            for i := lb + 1 until ub do writeon( i_w := 1, s_w := 0, "," , v( i ) )
        end;
        writeon( s_w := 0, "]" )
    end printArray ;
    begin
        integer array v ( 1 :: 9 );
        for i := 1 until 9 do v( i ) := i; 
        printArray( v, 1, 9 );
        writeon( " -> " );
        rotateLeft( v, 1, 9, 3 );
        printArray( v, 1, 9 );
        write()
    end
end.

Output:

[1,2,3,4,5,6,7,8,9] -> [4,5,6,7,8,9,1,2,3]

AppleScript

Functional

Prefix appended

------------- SHIFT LIST ELEMENTS TO LEFT BY 3 -----------

-- rotated :: Int -> [a] -> [a]
on rotated(n, xs)
    if 0 ≠ n then
        set m to |mod|(n, length of xs)
        
        (items (1 + m) thru -1 of xs) & ¬
            (items 1 thru m of xs)
    else
        xs
    end if
end rotated


--------------------------- TEST -------------------------
on run
    set xs to {1, 2, 3, 4, 5, 6, 7, 8, 9}
    
    unlines({"     Input list: " & showList(xs), ¬
        " Rotated 3 left: " & showList(rotated(3, xs)), ¬
        "Rotated 3 right: " & showList(rotated(-3, xs))})
end run


------------------------- GENERIC ------------------------

-- mod :: Int -> Int -> Int
on |mod|(n, d)
    -- The built-in infix `mod` inherits the sign of the 
    -- *dividend* for non zero results. 
    -- (i.e. the 'rem' pattern in some languages).
    --
    -- This version inherits the sign of the *divisor*.
    -- (A more typical 'mod' pattern, and useful,
    -- for example, with biredirectional list rotations).
    if signum(n) = signum(-d) then
        (n mod d) + d
    else
        (n mod d)
    end if
end |mod|


-- signum :: Num -> Num
on signum(x)
    if x < 0 then
        -1
    else if x = 0 then
        0
    else
        1
    end if
end signum


------------------------ FORMATTING ----------------------

-- intercalate :: String -> [String] -> String
on intercalate(delim, xs)
    set {dlm, my text item delimiters} to ¬
        {my text item delimiters, delim}
    set s to xs as text
    set my text item delimiters to dlm
    s
end intercalate


-- map :: (a -> b) -> [a] -> [b]
on map(f, xs)
    -- The list obtained by applying f
    -- to each element of 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 |λ|(item i of xs, i, xs)
        end repeat
        return lst
    end tell
end map


-- 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


-- showList :: [a] -> String
on showList(xs)
    "{" & intercalate(", ", map(my str, xs)) & "}"
end showList


-- str :: a -> String
on str(x)
    x as string
end str


-- 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 s to xs as text
    set my text item delimiters to dlm
    s
end unlines

Output:

     Input list: {1, 2, 3, 4, 5, 6, 7, 8, 9}
 Rotated 3 left: {4, 5, 6, 7, 8, 9, 1, 2, 3}
Rotated 3 right: {7, 8, 9, 1, 2, 3, 4, 5, 6}

Cycle sampled

Another approach: drawing from an infinite list of cycles:

------------- SHIFT LIST ELEMENTS TO LEFT BY 3 -----------

-- rotated :: Int -> [a] -> [a]
on rotated(n, xs)
    set m to length of xs
    
    take(m, drop(|mod|(n, m), cycle(xs)))
end rotated


--------------------------- TEST -------------------------
on run
    set xs to {1, 2, 3, 4, 5, 6, 7, 8, 9}
    
    unlines({"      Input list: " & showList(xs), "", ¬
        " Rotated  3 left: " & showList(rotated(3, xs)), ¬
        "                  " & showList(rotated(30, xs)), ¬
        " Rotated 3 right: " & showList(rotated(-3, xs)), ¬
        "                  " & showList(rotated(-30, xs))})
end run


------------------------- GENERIC ------------------------

-- cycle :: [a] -> Generator [a]
on cycle(xs)
    script
        property lng : 1 + (length of xs)
        property i : missing value
        on |λ|()
            if missing value is i then
                set i to 1
            else
                set nxt to (1 + i) mod lng
                if 0 = ((1 + i) mod lng) then
                    set i to 1
                else
                    set i to nxt
                end if
            end if
            return item i of xs
        end |λ|
    end script
end cycle


-- drop :: Int -> [a] -> [a]
-- drop :: Int -> String -> String
on drop(n, xs)
    set c to class of xs
    if script is not c then
        if string is not c then
            if n < length of xs then
                items (1 + n) thru -1 of xs
            else
                {}
            end if
        else
            if n < length of xs then
                text (1 + n) thru -1 of xs
            else
                ""
            end if
        end if
    else
        take(n, xs) -- consumed
        return xs
    end if
end drop


-- mod :: Int -> Int -> Int
on |mod|(n, d)
    -- The built-in infix `mod` inherits the sign of the 
    -- *dividend* for non zero results. 
    -- (i.e. the 'rem' pattern in some languages).
    --
    -- This version inherits the sign of the *divisor*.
    -- (A more typical 'mod' pattern, and useful,
    -- for example, with biredirectional list rotations).
    if signum(n) = signum(-d) then
        (n mod d) + d
    else
        (n mod d)
    end if
end |mod|


-- signum :: Num -> Num
on signum(x)
    if x < 0 then
        -1
    else if x = 0 then
        0
    else
        1
    end if
end signum


-- take :: Int -> [a] -> [a]
-- take :: Int -> String -> String
on take(n, xs)
    set c to class of xs
    if list is c then
        set lng to length of xs
        if 0 < n and 0 < lng then
            items 1 thru min(n, lng) of xs
        else
            {}
        end if
    else if string is c then
        if 0 < n then
            text 1 thru min(n, length of xs) of xs
        else
            ""
        end if
    else if script is c then
        set ys to {}
        repeat with i from 1 to n
            set v to |λ|() of xs
            if missing value is v then
                return ys
            else
                set end of ys to v
            end if
        end repeat
        return ys
    else
        missing value
    end if
end take


------------------------ FORMATTING ----------------------

-- intercalate :: String -> [String] -> String
on intercalate(delim, xs)
    set {dlm, my text item delimiters} to ¬
        {my text item delimiters, delim}
    set s to xs as text
    set my text item delimiters to dlm
    s
end intercalate


-- map :: (a -> b) -> [a] -> [b]
on map(f, xs)
    -- The list obtained by applying f
    -- to each element of 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 |λ|(item i of xs, i, xs)
        end repeat
        return lst
    end tell
end map


-- 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


-- showList :: [a] -> String
on showList(xs)
    "{" & intercalate(", ", map(my str, xs)) & "}"
end showList


-- str :: a -> String
on str(x)
    x as string
end str


-- 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 s to xs as text
    set my text item delimiters to dlm
    s
end unlines

Output:

      Input list: {1, 2, 3, 4, 5, 6, 7, 8, 9}

 Rotated  3 left: {4, 5, 6, 7, 8, 9, 1, 2, 3}
                  {4, 5, 6, 7, 8, 9, 1, 2, 3}
 Rotated 3 right: {7, 8, 9, 1, 2, 3, 4, 5, 6}
                  {7, 8, 9, 1, 2, 3, 4, 5, 6}

Two in-place alternatives

Fewest moves:

(* List range rotation, in-place with temporary external storage. Negative 'amount' = left rotation, positive = right.
    Method:
        Adjust the specified amount to get a positive, < list length, left-rotation figure.
        Store the range's leftmost 'amount' items.
        Move the range's other items 'amount' places to the left.
        Move the stored items into the range's rightmost slots.
*)
on rotate(theList, l, r, amount)
    set listLength to (count theList)
    if (listLength < 2) then return
    if (l < 0) then set l to listLength + l + 1
    if (r < 0) then set r to listLength + r + 1
    if (l > r) then set {l, r} to {r, l}
    
    script o
        property lst : theList
        property storage : missing value
    end script
    
    set rangeLength to r - l + 1
    set amount to (rangeLength + rangeLength - amount) mod rangeLength
    if (amount is 0) then return
    set o's storage to o's lst's items l thru (l + amount - 1)
    repeat with i from (l + amount) to r
        set o's lst's item (i - amount) to o's lst's item i
    end repeat
    set j to r - amount
    repeat with i from 1 to amount
        set o's lst's item (j + i) to o's storage's item i
    end repeat
end rotate

-- Task code:
local lst
set lst to {1, 2, 3, 4, 5, 6, 7, 8, 9}
-- Left-rotate all items (1 thru -1) by three places.
rotate(lst, 1, -1, -3)
return lst

Wholly in-place:

(* List range rotation, wholly in-place. Negative 'amount' = left rotation, positive = right.
    Method:
        Adjust the specified rotation amount to get a positive, < list length, left-rotation figure.
        If rotating by only 1 in either direction, do it in the obvious way.
        Otherwise reverse the range's leftmost 'amount' items, reverse the others, then reverse the lot.
*)
on rotate(theList, l, r, amount)
    set listLength to (count theList)
    if (listLength < 2) then return
    if (l < 0) then set l to listLength + l + 1
    if (r < 0) then set r to listLength + r + 1
    if (l > r) then set {l, r} to {r, l}
    
    script o
        property lst : theList
        
        on rotate1(a, z, step)
            set v to my lst's item a
            repeat with i from (a + step) to z by step
                set my lst's item (i - step) to my lst's item i
            end repeat
            set my lst's item z to v
        end rotate1
        
        on |reverse|(i, j)
            repeat with i from i to ((i + j - 1) div 2)
                set v to my lst's item i
                set my lst's item i to my lst's item j
                set my lst's item j to v
                set j to j - 1
            end repeat
        end |reverse|
    end script
    
    set rangeLength to r - l + 1
    set amount to (rangeLength + rangeLength - amount) mod rangeLength
    if (amount is 1) then
        tell o to rotate1(l, r, 1) -- Rotate left by 1.
    else if (amount = rangeLength - 1) then
        tell o to rotate1(r, l, -1) -- Rotate right by 1.
    else if (amount > 0) then
        tell o to |reverse|(l, l + amount - 1)
        tell o to |reverse|(l + amount, r)
        tell o to |reverse|(l, r)
    end if
end rotate

-- Task code:
local lst
set lst to {1, 2, 3, 4, 5, 6, 7, 8, 9}
-- Left-rotate all items (1 thru -1) by three places.
rotate(lst, 1, -1, -3)
return lst

Result in both cases:

Output:

{4, 5, 6, 7, 8, 9, 1, 2, 3}

Arturo

lst: [1 2 3 4 5 6 7 8 9]
print rotate.left lst 3

Output:

4 5 6 7 8 9 1 2 3

AutoHotkey

Shift_list_elements(Arr, dir, n){
    nums := Arr.Clone()
    loop % n
        if InStr(dir, "l")
            nums.Push(nums.RemoveAt(1))
        else
            nums.InsertAt(1, nums.RemoveAt(nums.count()))
    return nums
}

Examples:

Arr  := [1,2,3,4,5,6,7,8,9]
output1 := Shift_list_elements(Arr, "L", 3)
output2 := Shift_list_elements(Arr, "R", 3)
return

Output:

output1 = [4, 5, 6, 7, 8, 9, 1, 2, 3]
output2 = [7, 8, 9, 1, 2, 3, 4, 5, 6]

AWK

# syntax: GAWK -f SHIFT_LIST_ELEMENTS_TO_LEFT_BY_3.AWK
BEGIN {
    list = "1,2,3,4,5,6,7,8,9"
    printf("old: %s\n",list)
    printf("new: %s\n",shift_left(list,3))
    list = "a;b;c;d"
    printf("old: %s\n",list)
    printf("new: %s\n",shift_left(list,1,";"))
    exit(0)
}
function shift_left(str,n,sep,  i,left,right) {
    if (sep == "") {
      sep = ","
    }
    for (i=1; i<=n; i++) {
      left = substr(str,1,index(str,sep)-1)
      right = substr(str,index(str,sep)+1)
      str = right sep left
    }
    return(str)
}

Output:

old: 1,2,3,4,5,6,7,8,9
new: 4,5,6,7,8,9,1,2,3
old: a;b;c;d
new: b;c;d;a

BASIC

BASIC256

arraybase 1
global lista
dim lista(9)
lista[1] = 1
lista[2] = 2
lista[3] = 3
lista[4] = 4
lista[5] = 5
lista[6] = 6
lista[7] = 7
lista[8] = 8
lista[9] = 9

subroutine shiftLeft (lista)
	lo = lista[?,]
	hi = lista[?]
	first = lista[lo]
	for i = lo to hi-1
		lista[i] = lista[i + 1]
	next i
	lista[hi] = first
end subroutine

subroutine shiftLeftN (lista, n)
	for i = 1 to n
		call shiftLeft(lista)
	next i
end subroutine

call shiftLeftN(lista, 3)

for i = 1 to 9
	print lista[i];
	if i < 9 then print ", ";
next i
end

Output:

Igual que la entrada de FreeBASIC.

PureBasic

Global Dim lista.i(9)

DataSection
  Data.i 1,2,3,4,5,6,7,8,9
EndDataSection
For i.i = 1 To 9
  Read lista(i)
Next i

Procedure shiftLeft (lista)
  ;shifts list left by one step
  lo.i =  1 ;ArraySize(lista(), 1)
  hi.i =  ArraySize(lista())
  first.i = lista(lo)
  For i.i = lo To hi-1
    lista(i) = lista(i + 1)
  Next i
  lista(hi) = first
EndProcedure

Procedure shiftLeftN (lista, n)
  For i.i = 1 To n
    shiftLeft(lista)
  Next i
EndProcedure

OpenConsole()
shiftLeftN(lista, 3)

For i.i = 1 To 9
  Print(Str(lista(i)))
  If i < 9 : Print(", ") : EndIf
Next i
Input()
CloseConsole()

Output:

Igual que la entrada de FreeBASIC.

QBasic

DIM SHARED lista(1 TO 9)
DATA 1,2,3,4,5,6,7,8,9
FOR i = 1 TO 9
    READ lista(i)
NEXT i

SUB shiftLeft (lista())
    lo = LBOUND(lista)
    hi = UBOUND(lista)
    first = lista(lo)
    FOR i = lo TO hi
	lista(i) = lista(i + 1)
    NEXT i
    lista(hi) = first
END SUB

SUB shiftLeftN (lista(), n)
    FOR i = 1 TO n
	CALL shiftLeft(lista())
	NEXT i
END SUB

CALL shiftLeftN(lista(), 3)

FOR i = 1 TO 9
    PRINT lista(i);
    IF i < 9 THEN PRINT ", ";
NEXT i
END

Output:

Igual que la entrada de FreeBASIC.

C

Translation of: Wren

#include <stdio.h>

/* in place left shift by 1 */
void lshift(int *l, size_t n) {
    int i, f;
    if (n < 2) return;
    f = l[0];
    for (i = 0; i < n-1; ++i) l[i] = l[i+1];
    l[n-1] = f;
}

int main() {
    int l[] = {1, 2, 3, 4, 5, 6, 7, 8, 9};
    int i;
    size_t n = 9;
    printf("Original list     : ");
    for (i = 0; i < n; ++i) printf("%d ", l[i]);
    printf("\nShifted left by 3 : ");
    for (i = 0; i < 3; ++i) lshift(l, n);
    for (i = 0; i < n; ++i) printf("%d ", l[i]);
    printf("\n");
    return 0;
}

Output:

Original list     : 1 2 3 4 5 6 7 8 9 
Shifted left by 3 : 4 5 6 7 8 9 1 2 3 

C++

#include <algorithm>
#include <iostream>
#include <iterator>
#include <vector>

template <typename T>
void print(const std::vector<T>& v) {
    std::copy(v.begin(), v.end(), std::ostream_iterator<T>(std::cout, " "));
    std::cout << '\n';
}

int main() {
    std::vector<int> vec{1, 2, 3, 4, 5, 6, 7, 8, 9};
    std::cout << "Before: ";
    print(vec);
    std::rotate(vec.begin(), vec.begin() + 3, vec.end());
    std::cout << " After: ";
    print(vec);
}

Output:

Before: 1 2 3 4 5 6 7 8 9 
 After: 4 5 6 7 8 9 1 2 3 

CLU

% Shift an array left by a certain amount
shift_left = proc [T: type] (a: array[T], n: int)
    at = array[T]
    % shifting an empty array is a no-op
    if at$empty(a) then return end 
    
    % otherwise we take elements from the bottom
    % and put them at the top 
    low: int := at$low(a)
    for i: int in int$from_to(1, n) do
        at$addh(a, at$reml(a))
    end
    at$set_low(a, low)
end shift_left

show = proc (s: stream, a: array[int])
    for i: int in array[int]$elements(a) do
        stream$puts(s, int$unparse(i) || " ")
    end
    stream$putc(s,'\n')
end show

start_up = proc ()
    po: stream := stream$primary_output()
    arr: array[int] := array[int]$[1,2,3,4,5,6,7,8,9]
    
    stream$puts(po, "Before: ") show(po, arr)
    shift_left[int](arr, 3)
    stream$puts(po, " After: ") show(po, arr)
end start_up

Output:

Before: 1 2 3 4 5 6 7 8 9
 After: 4 5 6 7 8 9 1 2 3

Common Lisp

;; Load the alexandria library from the quicklisp repository
CL-USER> (ql:quickload "alexandria")

CL-USER> (alexandria:rotate '(1 2 3 4 5 6 7 8 9) -3)
(4 5 6 7 8 9 1 2 3)

Delphi

Library: System.SysUtils

Library: Boost.Int

Boost.Int is part of DelphiBoostLib.

program Shift_list_elements_to_left_by_3;

{$APPTYPE CONSOLE}

uses
  System.SysUtils,
  Boost.Int;

var
  List: TArray<Integer>;

begin
  List := [1, 2, 3, 4, 5, 6, 7, 8, 9];
  writeln('Original list     :', list.ToString);
  List.shift(3);
  writeln('Shifted left by 3 :', list.ToString);
  Readln;
end.

Output:

Original list     :[1, 2, 3, 4, 5, 6, 7, 8, 9]
Shifted left by 3 :[4, 5, 6, 7, 8, 9, 1, 2, 3]

Elixir

def rotate(enumerable, count) do
  {left, right} = Enum.split(enumerable, count)
  right ++ left
end

rotate(1..9, 3)
# [4, 5, 6, 7, 8, 9, 1, 2, 3]

Euler

begin
    new shl; new shl3;

    shl  <- ` formal ls;
              if length ls < 2 then ls
                               else begin
                                        new L;
                                        L <- ls;
                                        tail L & ( L[ 1 ] )
                                    end
            ';
    shl3 <- ` formal ls; shl( shl( shl( ls ) ) ) ';

    out shl3( ( 1, 2, 3, 4, 5, 6, 7, 8 ) )
end
$

Excel

LAMBDA

Binding the name rotatedRow to the following lambda expression in the Name Manager of the Excel WorkBook:

(See LAMBDA: The ultimate Excel worksheet function)

Works with: Office 365 betas 2021

rotatedRow
=LAMBDA(n,
    LAMBDA(xs,
        LET(
            nCols, COLUMNS(xs),
            m, MOD(n, nCols),
            x, SEQUENCE(
                1, nCols,
                1, 1
            ),
            d, nCols - m,

            IF(x > d,
                x - d,
                m + x
            )
        )
    )
)

Output:

The formula in cell B2 defines an array which populates the whole range B2:J2

	fx	=rotatedRow(3)(B1#)
	A	B	C	D	E	F	G	H	I	J
1	List	1	2	3	4	5	6	7	8	9
2	Rotated	4	5	6	7	8	9	1	2	3

Or, in terms of the MAKEARRAY function:

rotated
=LAMBDA(n,
    LAMBDA(xs,
        LET(
            nCols, COLUMNS(xs),
            m, MOD(n, nCols),
            d, nCols - m,
            
            MAKEARRAY(
                1, nCols,
                LAMBDA(
                    _, x,
                    IF(d < x,
                        x - d,
                        m + x
                    )
                )
            )
        )
    )
)

Output:

	fx	=rotated(3)(B1#)
	A	B	C	D	E	F	G	H	I	J
1	List	1	2	3	4	5	6	7	8	9
2	Rotated	4	5	6	7	8	9	1	2	3

F#

// Nigel Gallowy. March 29th., 2021
let fN=function _::_::_::n->n |_->raise(System.Exception("List has fewer than 3 elements"))
[[1..10];[1;2];[1;2;3]]|>Seq.iter(fun n->try printfn "%A->%A" n (fN n) with :? System.Exception as e->printfn "oops -> %s" (e.Message))

Output:

[1; 2; 3; 4; 5; 6; 7; 8; 9; 10]->[4; 5; 6; 7; 8; 9; 10]
oops -> List has fewer than 3 elements
[1; 2; 3]->[]

Factor

 USING: prettyprint sequences.extras ;

{ 1 2 3 4 5 6 7 8 9 } 3 rotate .

Output:

{ 4 5 6 7 8 9 1 2 3 }

You can also make a virtual rotated sequence. In other words, the underlying array remains the same, but the way it is indexed has been changed.

USING: arrays prettyprint sequences.rotated ;

{ 1 2 3 4 5 6 7 8 9 } 3 <rotated> >array .

Output:

{ 4 5 6 7 8 9 1 2 3 }

FreeBASIC

sub shift_left( list() as integer )
    'shifts list left by one step
    dim as integer lo = lbound(list), hi = ubound(list), first
    first = list(lo)
    for i as integer = lo to hi
        list(i) = list(i+1)
    next i
    list(hi) = first
    return
end sub

sub shift_left_n( list() as integer, n as uinteger )
    for i as uinteger = 1 to n
        shift_left( list() )
    next i
    return
end sub

dim as integer list(1 to 9) = {1,2,3,4,5,6,7,8,9}
shift_left_n( list(), 3 )
for i as integer = 1 to 9
    print list(i);
    if i<9 then print ", ";
next i

Output:

4, 5, 6, 7, 8, 9, 1, 2, 3

Go

Translation of: Wren

package main

import "fmt"

// in place left shift by 1
func lshift(l []int) {
    n := len(l)
    if n < 2 {
        return
    }
    f := l[0]
    for i := 0; i < n-1; i++ {
        l[i] = l[i+1]
    }
    l[n-1] = f
}

func main() {
    l := []int{1, 2, 3, 4, 5, 6, 7, 8, 9}
    fmt.Println("Original list     :", l)
    for i := 0; i < 3; i++ {
        lshift(l)
    }
    fmt.Println("Shifted left by 3 :", l)
}

Output:

Original list     : [1 2 3 4 5 6 7 8 9]
Shifted left by 3 : [4 5 6 7 8 9 1 2 3]

Haskell

------------- SHIFT LIST ELEMENTS TO LEFT BY N -----------

rotated :: Int -> [a] -> [a]
rotated n =
  ( (<*>) take
      . flip (drop . mod n)
      . cycle
  )
    <*> length

--------------------------- TEST -------------------------
main :: IO ()
main =
  let xs = [1 .. 9]
   in putStrLn ("Initial list: " <> show xs <> "\n")
        >> putStrLn "Rotated 3 or 30 positions to the left:"
        >> print (rotated 3 xs)
        >> print (rotated 30 xs)
        >> putStrLn "\nRotated 3 or 30 positions to the right:"
        >> print (rotated (-3) xs)
        >> print (rotated (-30) xs)

Output:

Initial list: [1,2,3,4,5,6,7,8,9]

Rotated 3 or 30 positions to the left:
[4,5,6,7,8,9,1,2,3]
[4,5,6,7,8,9,1,2,3]

Rotated 3 or 30 positions to the right:
[7,8,9,1,2,3,4,5,6]
[7,8,9,1,2,3,4,5,6]

J

   3 |. 1 2 3 4 5 6 7 8 9
4 5 6 7 8 9 1 2 3

However, while this matches the task example, it does not match the task title. In most contexts, a shift is different from a rotate:

   3 |.(!.0) 1 2 3 4 5 6 7 8 9
4 5 6 7 8 9 0 0 0

Java

import java.util.List;
import java.util.Arrays;
import java.util.Collections;

public class RotateLeft {
    public static void main(String[] args) {
        List<Integer> list = Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8, 9);
        System.out.println("original: " + list);
        Collections.rotate(list, -3);
        System.out.println("rotated: " + list);
    }
}

Output:

original: [1, 2, 3, 4, 5, 6, 7, 8, 9]
rotated: [4, 5, 6, 7, 8, 9, 1, 2, 3]

JavaScript

(() => {
    "use strict";

    // -------- SHIFT LIST ELEMENTS TO LEFT BY 3 ---------

    // rotated :: Int -> [a] -> [a]
    const rotated = n =>
        // A rotation, n elements to the left,
        // of the input list.
        xs => 0 !== n ? (() => {
            const m = mod(n)(xs.length);

            return xs.slice(m).concat(
                xs.slice(0, m)
            );
        })() : Array.from(xs);


    // ---------------------- TEST -----------------------
    // main :: IO ()
    const main = () => {
        const xs = [1, 2, 3, 4, 5, 6, 7, 8, 9];

        return [
                `    The input list: ${show(xs)}`,
                ` rotated 3 to left: ${show(rotated(3)(xs))}`,
                `     or 3 to right: ${show(rotated(-3)(xs))}`
            ]
            .join("\n");
    };

    // --------------------- GENERIC ---------------------

    // mod :: Int -> Int -> Int
    const mod = n =>
        // Inherits the sign of the *divisor* for non zero
        // results. Compare with `rem`, which inherits
        // the sign of the *dividend*.
        d => (n % d) + (
            signum(n) === signum(-d) ? (
                d
            ) : 0
        );


    // signum :: Num -> Num
    const signum = n =>
        0 > n ? (
            -1
        ) : (
            0 < n ? 1 : 0
        );


    // show :: a -> String
    const show = x =>
        JSON.stringify(x);

    // MAIN ---
    return main();
})();

Output:

    The input list: [1,2,3,4,5,6,7,8,9]
 rotated 3 to left: [4,5,6,7,8,9,1,2,3]
     or 3 to right: [7,8,9,1,2,3,4,5,6]

jq

Works with: jq

Works with gojq, the Go implementation of jq

# input should be an array or string
def rotateLeft($n):
   .[$n:] + .[:$n];

Examples:

[1, 2, 3, 4, 5, 6, 7, 8, 9] | rotateLeft(3) #=> [4,5,6,7,8,9,1,2,3]

"123456789" | rotateLeft(3) #=> "456789123"

Julia

list = [1, 2, 3, 4, 5, 6, 7, 8, 9]
println(list, " => ", circshift(list, -3))

Output:

[1, 2, 3, 4, 5, 6, 7, 8, 9] => [4, 5, 6, 7, 8, 9, 1, 2, 3]

Mathematica/Wolfram Language

RotateLeft[{1, 2, 3, 4, 5, 6, 7, 8, 9}, 3]

Output:

{4, 5, 6, 7, 8, 9, 1, 2, 3}

Nim

Using “rotatedLeft” from standard module “algorithm”. Note that its exists also “rotateLeft” for rotation in place.

import algorithm

let list = @[1, 2, 3, 4, 5, 6, 7, 8, 9]
echo list, " → ", rotatedLeft(list, 3)

Output:

@[1, 2, 3, 4, 5, 6, 7, 8, 9] → @[4, 5, 6, 7, 8, 9, 1, 2, 3]

OCaml

At the REPL:

# let rec rotate n = function
    | h :: (_ :: _ as t) when n > 0 -> rotate (pred n) (t @ [h])
    | l -> l
  ;;
val rotate : int -> 'a list -> 'a list = <fun>
# rotate 3 [1; 2; 3; 4; 5; 6; 7; 8; 9] ;;
- : int list = [4; 5; 6; 7; 8; 9; 1; 2; 3]

Perl

// 20210315 Perl programming solution

use strict;
use warnings;

my $n = 3;
my @list = 1..9;

push @list, splice @list, 0, $n;

print join ' ', @list, "\n"

Output:

4 5 6 7 8 9 1 2 3

Phix

sequence s = {1,2,3,4,5,6,7,8,9}
s = s[4..$]&s[1..3]
?s

Output:

{4,5,6,7,8,9,1,2,3}

PicoLisp

(let L (range 1 9)
   (println (conc (tail -3 L) (head 3 L))) )

Python

def rotate(list, n):
    for _ in range(n):
        list.append(list.pop(0))

    return list

# or, supporting opposite direction rotations:

def rotate(list, n):
    k = (len(list) + n) % len(list)
    return list[k::] + list[:k:]


list = [1,2,3,4,5,6,7,8,9]
print(list, " => ", rotate(list, 3))

Output:

[1, 2, 3, 4, 5, 6, 7, 8, 9]  =>  [4, 5, 6, 7, 8, 9, 1, 2, 3]

and we can also define rotated lists and ranges as slices taken from an infinite cycle of their values, after n initial items have been dropped:

'''Shift list elements to left by 3'''

from itertools import cycle, islice


# rotated :: Int -> [a] -> [a]
def rotated(n):
    '''A list rotated n elements to the left.'''
    def go(xs):
        lng = len(xs)
        stream = cycle(xs)

        # (n modulo lng) elements dropped from the start,
        list(islice(stream, n % lng))

        # and lng elements drawn from the remaining cycle.
        return list(islice(stream, lng))
    return go


# ------------------------- TEST -------------------------
# main :: IO ()
def main():
    '''Positive and negative (left and right)
       rotations tested for list and range inputs.
    '''
    xs = [1, 2, 3, 4, 5, 6, 7, 8, 9]

    print("List rotated 3 positions to the left:")
    print(
        rotated(3)(xs)
    )
    print("List rotated 3 positions to the right:")
    print(
        rotated(-3)(xs)
    )
    print("\nLists obtained by rotations of an input range:")
    rng = range(1, 1 + 9)
    print(
        rotated(3)(rng)
    )
    print(
        rotated(-3)(rng)
    )


# MAIN ---
if __name__ == '__main__':
    main()

Output:

List rotated 3 positions to the left:
[4, 5, 6, 7, 8, 9, 1, 2, 3]
List rotated 3 positions to the right:
[7, 8, 9, 1, 2, 3, 4, 5, 6]

Lists obtained by rotations of an input range:
[4, 5, 6, 7, 8, 9, 1, 2, 3]
[7, 8, 9, 1, 2, 3, 4, 5, 6]

Quackery

' [ 1 2 3 4 5 6 7 8 9 ] 3 split swap join echo

Output:

[ 4 5 6 7 8 9 1 2 3 ]

Raku

# 20210315 Raku programming solution

say [1..9].rotate(3)

Output:

(4 5 6 7 8 9 1 2 3)

REXX

/*REXX program  shifts  (using a rotate)  elements in a list  left  by some number  N.  */
parse arg n $ .                                  /*obtain optional arguments from the CL*/
if n=='' | n==","  then n= 3                     /*Not specified?  Then use the default.*/
if $=='' | $==","  then $= '[1,2,3,4,5,6,7,8,9]' /* "      "         "   "   "     "    */

$$= space( translate($, , '],[') )               /*convert literal list to bare list.   */
$$= '['translate( subword($$, N+1)  subword($$, 1, n), ',', " ")']'   /*rotate the list.*/

say 'shifting elements in the list by '  n       /*display action used on the input list*/
say ' input list='   $                           /*   "    the  input list ───► terminal*/
say 'output list='  $$                           /*   "    the output   "    "      "   */

output   when using the default inputs:

shifting elements in the list by  3
 input list= [1,2,3,4,5,6,7,8,9]
output list= [4,5,6,7,8,9,1,2,3]

Ring

see "working..." + nl

shift = [1,2,3,4,5,6,7,8,9]
lenshift = len(shift)
shiftNew = list(lenshift)
nshift = 3
temp = list(nshift)

see "original list:" + nl
showArray(shift)
see nl + "Shifted left by 3:" + nl

for n = 1 to nshift
    temp[n] = shift[n]
next

for n = 1 to lenshift - nshift
    shiftNew[n] = shift[n+nshift]
next

for n = lenshift-nshift+1 to lenshift
    shiftNew[n] = temp[n-lenshift+nshift]
next

showArray(shiftNew)

see nl + "done..." + nl

func showArray(array)
     txt = "["
     for n = 1 to len(array)
         txt = txt + array[n] + ", "
     next
     txt = left(txt,len(txt)-2)
     txt = txt + "]"
     see txt

Output:

working...
original list:
[1, 2, 3, 4, 5, 6, 7, 8, 9]
shifted left by 3:
[4, 5, 6, 7, 8, 9, 1, 2, 3]
done...

RPL

≪ LIST→ → size 
  ≪ 1 3 START size ROLL NEXT
    size →LIST
≫ ≫
'SLL3' STO

{ 1 2 3 4 5 6 7 8 } SLL3

Output:

1: { 4 5 6 7 8 1 2 3 }

Ruby

Note, unlike some other languages, for Ruby's Array.rotate() method, a positive number means rotate to the left, while a negative number means rotate to the right. Use Array.rotate!() if you wish to mutate the original array rather than return a new one.

list = [1,2,3,4,5,6,7,8,9]
p list.rotate(3)

Output:

[4, 5, 6, 7, 8, 9, 1, 2, 3]

Rust

fn main() {
    let mut v = vec![1, 2, 3, 4, 5, 6, 7, 8, 9];
    println!("Before: {:?}", v);
    v.rotate_left(3);
    println!(" After: {:?}", v);
}

Output:

Before: [1, 2, 3, 4, 5, 6, 7, 8, 9]
 After: [4, 5, 6, 7, 8, 9, 1, 2, 3]

Scheme

Works with: Chez Scheme

; Rotate a list by the given number of elements.
; Positive = Rotate left; Negative = Rotate right.

(define list-rotate
  (lambda (lst n)
    (cond
      ((or (not (pair? lst)) (= n 0))
        lst)
      ((< n 0)
        (let ((end (1- (length lst))))
          (list-rotate (append (list (list-ref lst end)) (list-head lst end)) (1+ n))))
      (else
        (list-rotate (cdr (append lst (list (car lst)))) (1- n))))))

Output:

(list-rotate '(1 2 3 4 5 6 7 8 9) 3) --> (4 5 6 7 8 9 1 2 3)
(list-rotate '(1 2 3 4 5 6 7 8 9) -3) --> (7 8 9 1 2 3 4 5 6)

sed

# rotate in 3 steps to easily work with lengths < 4
s/^\([^,]*\),\(.*\)/\2,\1/
s/^\([^,]*\),\(.*\)/\2,\1/
s/^\([^,]*\),\(.*\)/\2,\1/

Output:

$ echo 1,2,3,4,5,6,7,8,9 | sed -f rotate.sed
4,5,6,7,8,9,1,2,3

Wren

// in place left shift by 1
var lshift = Fn.new { |l|
    var n = l.count
    if (n < 2) return
    var f = l[0]
    for (i in 0..n-2) l[i] = l[i+1]
    l[-1] = f
}

var l = (1..9).toList
System.print("Original list     : %(l)")
for (i in 1..3) lshift.call(l)
System.print("Shifted left by 3 : %(l)")

Output:

Original list     : [1, 2, 3, 4, 5, 6, 7, 8, 9]
Shifted left by 3 : [4, 5, 6, 7, 8, 9, 1, 2, 3]

Library: Wren-seq

Alternatively, using a library method to produce the same output as before.

import "./seq" for Lst
 
var l = (1..9).toList
System.print("Original list     : %(l)")
System.print("Shifted left by 3 : %(Lst.lshift(l, 3))")

XPL0

int A, N, T, I;
[A:= [1, 2, 3, 4, 5, 6, 7, 8, 9];
for N:= 1 to 3 do  \rotate A left 3 places
    [T:= A(0);
    for I:= 0 to 9-2 do A(I):= A(I+1);
    A(I):= T];
for I:= 0 to 9-2 do
    [IntOut(0, A(I));  Text(0, ", ")];
IntOut(0, A(I));
]

Output:

4, 5, 6, 7, 8, 9, 1, 2, 3

Z80 Assembly

Zilog Z80

This example code will not work on the Game Boy, as the Game Boy does not have the RLD or RRD instructions.

The RLD instruction is a very peculiar one. It rotates leftward the bottom four bits of the accumulator with the byte pointed to by HL. For example, if A = &36 and (HL) = &BF, then a single RLD will result in A = &3B and (HL) = &F6. As it turns out, this can be used to rotate the entries in an array without using a ton of stack space.

PrintChar equ &BB5A ;address of Amstrad CPC firmware routine, writes accumulator to stdout.

org &1000
ld hl,myarray_end-1  ;HL must point to the last byte in the array.
ld b,9               ;byte count
call RLCA_RANGE

ld hl,myarray_end-1
ld b,9
call RLCA_RANGE

ld hl,myarray_end-1
ld b,9
call RLCA_RANGE

ld hl,myarray
jp PrintString
;ret

myarray:
;pre-convert these numbers to ascii so that the job is easier.
byte &31,&32,&33,&34,&35,&36,&37,&38,&39
myarray_end:
byte 0	;null terminator

RLCA_RANGE:		;DOESN'T WORK ON GAME BOY
;rotates a range of memory, e.g. &1000 = &23,&45,&67,&89 > &45,&67,&89,&23
;point HL at the end of the memory range this time.
	ld a,(hl)
	push hl
	push bc
loop_RLCA_RANGE_FIRST:
		RLD
		DEC HL
		djnz loop_RLCA_RANGE_FIRST
	pop bc
	pop hl
	
	push hl
	push bc
loop_RLCA_RANGE_SECOND:
		RLD
		DEC HL
		djnz loop_RLCA_RANGE_SECOND
	pop bc
	pop hl
	RLD
	ret

PrintString:
	ld a,(hl)
	or a
	ret z
	call PrintChar
	inc hl
	jr PrintString

Output:

456789123