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# Loops/Downward for

Loops/Downward for
You are encouraged to solve this task according to the task description, using any language you may know.

Write a   for   loop which writes a countdown from   10   to   0.

## 11l

`L(i) (10..0).step(-1)   print(i)`

## 360 Assembly

Use of BXLE and BCT opcodes.

`*        Loops/Downward for        27/07/2015LOOPDOWN CSECT                             USING  LOOPDOWN,R12         LR     R12,R15            set base registerBEGIN    EQU    **        fisrt loop with a BXLE    BXLE: Branch on indeX Low or Equal         LH     R2,=H'11'          from 10 (R2=11) index         LH     R4,=H'-1'          step -1 (R4=-1)         LH     R5,=H'-1'          to 0    (R5=-1)LOOPI    BXLE   R2,R4,ELOOPI       R2=R2+R4 if R2<=R5 goto ELOOPI         XDECO  R2,BUFFER          edit R2         XPRNT  BUFFER,L'BUFFER    print             B      LOOPIELOOPI   EQU    **        second loop with a BCT    BCT: Branch on CounT         LA     R2,10              index   R2=10         LA     R3,11              counter R3=11LOOPJ    XDECO  R2,BUFFER          edit R2         XPRNT  BUFFER,L'BUFFER    print         BCTR   R2,0               R2=R2-1ELOOPJ   BCT    R3,LOOPJ           R3=R3-1 if R3<>0 goto LOOPIRETURN   XR     R15,R15            set return code         BR     R14                return to callerBUFFER   DC     CL80' '         YREGS           END    LOOPDOWN`

## 6502 Assembly

Code is called as a subroutine (i.e. JSR Start). Printing routines are only partially coded here, specific OS/hardware routines for printing are left unimplemented.

`;An OS/hardware specific routine that is setup to display the Ascii character;value contained in the AccumulatorSend 		= 	\$9000		;routine not implemented herePrintNewLine	=	\$9050		;routine not implemented here   		*= 	\$8000		;set base address Start		PHA			;push Accumulator and Y register onto stack		TYA		PHA		LDY 	#10		;set Y register to loop start value		TYA			;place loop value in the Accumulator Loop		JSR	PrintTwoDigits		JSR   PrintNewLine		DEY			;decrement loop value		BPL	Loop		;continue loop if sign flag is clear		PLA			;pop Y register and Accumulator off of stack		TAY		PLA		RTS			;exit ;Print value in Accumulator as two hex digitsPrintTwoDigits		PHA 		LSR 		LSR 		LSR 		LSR 		JSR     PrintDigit		PLA 		AND     #\$0F		JSR     PrintDigit		RTS  ;Convert value in Accumulator to an Ascii hex digitPrintDigit		ORA	#\$30		JSR	Send		;routine not implemented here		RTS `

## 68000 Assembly

Code is called as a subroutine, i.e. "JSR ForLoop." OS/Hardware specific printing subroutines are unimplemented here.

`ForLoop:MOVE.W #10,D0loop:JSR Print_D0_As_Ascii  ;some routine that converts the digits of D0 into ascii characters and prints them to screen.DBRA D0,loop           ;repeat until D0.W = \$FFFFrts`

## 8086 Assembly

It is typically much easier for assembly languages to loop downwards than forwards, as they can do so without using a redundant equality check. The 8086's `LOOP` instruction will loop a section of code, using the `CX` register as the loop counter.

`       .model small ;.exe file, max 128 KB       .stack 1024  ;reserve 1 KB for the stack pointer.        .data        ;no data needed        .codestart: 	mov ax,0100h	;UNPACKED BCD "10"	mov cx,0Bh	;loop counter repeat_countdown:	call PrintBCD_IgnoreLeadingZeroes	sub ax,1	aas				;ascii adjust for subtraction, normally 0100h - 1 = 0FFh but this corrects it to 0009h	push ax		mov dl,13		mov ah,02h		int 21h 		mov dl,10		mov ah,02h		int 21h		;these 6 lines of code are the "new line" function	pop ax	loop repeat_countdown ;decrement CX and jump back to the label "repeat_countdown" if CX != 0   	mov ax,4C00h	int 21h			;return to DOS PrintBCD_IgnoreLeadingZeroes:	push ax		cmp ah,0		jz skipLeadingZero			or ah,30h         ;convert a binary-coded decimal quantity to an ASCII numeral			push dx			push ax				mov al,ah				mov ah,0Eh				int 10h	   ;prints AL to screen			pop ax			pop dxskipLeadingZero:		or al,30h		push dx		push ax			mov ah,0Eh			int 10h		   		pop ax		pop dx	pop ax	ret         end start ;EOF`

## AArch64 Assembly

Works with: as version Raspberry Pi 3B version Buster 64 bits
` /* ARM assembly AARCH64 Raspberry PI 3B *//*  program loopdownward64.s   */ /*******************************************//* Constantes file                         *//*******************************************//* for this file see task include a file in language AArch64 assembly*/.include "../includeConstantesARM64.inc" /*********************************//* Initialized data              *//*********************************/.dataszMessResult:  .asciz "Counter =  @ \n"      // message result /*********************************//* UnInitialized data            *//*********************************/.bss sZoneConv:              .skip 24/*********************************//*  code section                 *//*********************************/.text.global main main:                          // entry of program     mov x4,#101:                             // begin loop     mov x0,x4    ldr x1,qAdrsZoneConv       // display value    bl conversion10            // call decimal conversion    ldr x0,qAdrszMessResult    ldr x1,qAdrsZoneConv       // display value    bl strInsertAtCharInc      // insert result at @ character    bl affichageMess           // display message    subs x4,x4,1               // decrement counter    bge 1b                     // loop if greather 100:                           // standard end of the program     mov x0,0                   // return code    mov x8,EXIT                // request to exit program    svc 0                      // perform the system call qAdrsZoneConv:            .quad sZoneConvqAdrszMessResult:         .quad szMessResult/********************************************************//*        File Include fonctions                        *//********************************************************//* for this file see task include a file in language AArch64 assembly */.include "../includeARM64.inc" `

`for I in reverse 0..10 loop   Put_Line(Integer'Image(I));end loop;`

## Agena

Tested with Agena 2.9.5 Win32

`for i from 10 downto 0 do    print( i )od`

## ALGOL 60

Based on the 1962 Revised Repport on ALGOL:

``` begin
integer i;
for i:=10 step -1 until 0 do
outinteger(i)
end
```
Works with: ALGOL 60 version OS/360
`'BEGIN' 'COMMENT' Loops/Downward for - Algol60 - 23/06/2018;  'INTEGER' I;  'FOR' I := 10 'STEP' -1 'UNTIL' 0 'DO'     OUTINTEGER(1,I)'END'`

## ALGOL 68

Works with: ALGOL 68 version Standard - no extensions to language used
Works with: ALGOL 68G version Any - tested with release mk15-0.8b.fc9.i386
Works with: ELLA ALGOL 68 version Any (with appropriate job cards) - tested with release 1.8.8d.fc9.i386
`FOR i FROM 10 BY -1 TO 0 DO    print((i,new line))OD`

As a common extension the DOWNTO is sometimes included to optimise the loop termination logic. The DOWNTO is available in Marcel's ALGOL 68G and Cambridge ALGOL 68C.

`FOR i FROM 10 DOWNTO 0 DO    print((i,new line))OD`

## ALGOL W

`begin    for i := 10 step -1 until 0 do    begin        write( i )    endend.`

## Amazing Hopper

` #include <flow.h> DEF-MAIN   CLR-SCR   SET(i, 10)   LOOP(ciclo abajo)      PRNL(i)   BACK-IF-NOT-ZERO(i--, ciclo abajo)END `
Output:
```10
9
8
7
6
5
4
3
2
1
0
```

## AmigaE

`PROC main()  DEF i  FOR i := 10 TO 0 STEP -1    WriteF('\d\n', i)  ENDFORENDPROC`

## AppleScript

`repeat with i from 10 to 0 by -1  log iend repeat`

## ARM Assembly

Works with: as version Raspberry Pi
`  /* ARM assembly Raspberry PI  *//*  program loopdownward.s   */ /* Constantes    */.equ STDOUT, 1     @ Linux output console.equ EXIT,   1     @ Linux syscall.equ WRITE,  4     @ Linux syscall /*********************************//* Initialized data              *//*********************************/.dataszMessResult:  .ascii "Counter = "      @ message resultsMessValeur:   .fill 12, 1, ' '                   .asciz "\n"/*********************************//* UnInitialized data            *//*********************************/.bss /*********************************//*  code section                 *//*********************************/.text.global main main:                @ entry of program     push {fp,lr}      @ saves 2 registers     mov r4,#101:    @ begin loop     mov r0,r4    ldr r1,iAdrsMessValeur     @ display value    bl conversion10             @ call function with 2 parameter (r0,r1)    ldr r0,iAdrszMessResult    bl affichageMess            @ display message    subs r4,#1                   @ decrement counter    bge 1b                      @ loop if greather 100:   @ standard end of the program     mov r0, #0                  @ return code    pop {fp,lr}                 @restaur 2 registers    mov r7, #EXIT              @ request to exit program    svc #0                       @ perform the system call iAdrsMessValeur:          .int sMessValeuriAdrszMessResult:         .int szMessResult/******************************************************************//*     display text with size calculation                         */ /******************************************************************//* r0 contains the address of the message */affichageMess:    push {r0,r1,r2,r7,lr}      @ save  registres    mov r2,#0                  @ counter length 1:      @ loop length calculation     ldrb r1,[r0,r2]           @ read octet start position + index     cmp r1,#0                  @ if 0 its over     addne r2,r2,#1            @ else add 1 in the length     bne 1b                    @ and loop                                 @ so here r2 contains the length of the message     mov r1,r0        			@ address message in r1     mov r0,#STDOUT      		@ code to write to the standard output Linux     mov r7, #WRITE             @ code call system "write"     svc #0                      @ call systeme     pop {r0,r1,r2,r7,lr}        @ restaur des  2 registres */     bx lr                       @ return  /******************************************************************//*     Converting a register to a decimal                                 */ /******************************************************************//* r0 contains value and r1 address area   */conversion10:    push {r1-r4,lr}    @ save registers     mov r3,r1    mov r2,#10 1:	   @ start loop    bl divisionpar10 @ r0 <- dividende. quotient ->r0 reste -> r1    add r1,#48        @ digit	    strb r1,[r3,r2]  @ store digit on area    sub r2,#1         @ previous position    cmp r0,#0         @ stop if quotient = 0 */    bne 1b	          @ else loop    @ and move spaces in first on area    mov r1,#' '   @ space	2:	    strb r1,[r3,r2]  @ store space in area    subs r2,#1       @ @ previous position    bge 2b           @ loop if r2 >= zéro  100:	    pop {r1-r4,lr}    @ restaur registres     bx lr	          @return/***************************************************//*   division par 10   signé                       *//* Thanks to http://thinkingeek.com/arm-assembler-raspberry-pi/*  /* and   http://www.hackersdelight.org/            *//***************************************************//* r0 dividende   *//* r0 quotient */	/* r1 remainder  */divisionpar10:	  /* r0 contains the argument to be divided by 10 */    push {r2-r4}   /* save registers  */    mov r4,r0     mov r3,#0x6667   @ r3 <- magic_number  lower    movt r3,#0x6666  @ r3 <- magic_number  upper    smull r1, r2, r3, r0   @ r1 <- Lower32Bits(r1*r0). r2 <- Upper32Bits(r1*r0)     mov r2, r2, ASR #2     /* r2 <- r2 >> 2 */    mov r1, r0, LSR #31    /* r1 <- r0 >> 31 */    add r0, r2, r1         /* r0 <- r2 + r1 */    add r2,r0,r0, lsl #2   /* r2 <- r0 * 5 */    sub r1,r4,r2, lsl #1   /* r1 <- r4 - (r2 * 2)  = r4 - (r0 * 10) */    pop {r2-r4}    bx lr                  /* leave function */   `

## Arturo

`loop 10..0 'i [	print i]`
Output:
```10
9
8
7
6
5
4
3
2
1
0```

## Asymptote

Asymptote's control structures are similar to those in C, C++, or Java

`for(int i = 10; i >=0; --i) {    write(i);}`

## AutoHotkey

`x := 10While (x >= 0){  output .= "`n" . x  x--}MsgBox % output `

## Avail

`For each i from 10 to 0 by -1 do [Print: “i” ++ "\n";];`

Note that `10 to 0 by -1` section isn't a fixed part of the loop syntax, but a call to the `_to_by_` method, which returns a tuple of integers in a range separated by a particular step size, in this case returning `<10, 9, 8, 7, 6, 5, 4, 3, 2, 1>`.

## AWK

`BEGIN {  for(i=10; i>=0; i--) {     print i  }}`

## Axe

Axe does not support for loops with step sizes other than 1.

`For(I,0,10) Disp 10-I▶Dec,iEnd`

## BASIC

### Applesoft BASIC

`FOR I = 10 TO 0 STEP -1 : PRINT I : NEXT I`

### BaCon

`' Downward forFOR i = 10 DOWNTO 0 : PRINT i : NEXT`

### BASIC256

Works with: QBasic
`for i = 10 to 0 step -1	print i; " ";next iprintend`

### BBC BASIC

`      FOR i% = 10 TO 0 STEP -1        PRINT i%      NEXT`

### Commodore BASIC

`10 FOR I = 10 TO 0 STEP -120 PRINT I 30 NEXT`

### FreeBASIC

`' FB 1.05.0 Win64 For i As Integer = 10 To 0 Step -1  Print i; " ";NextPrint Sleep`
Output:
``` 10  9  8  7  6  5  4  3  2  1  0
```

### FutureBasic

` window 1, @"Countdown", ( 0, 0, 400, 300 ) NSInteger i for i = 10 to 0 step -1print inext HandleEvents `

Output:

``` 10
9
8
7
6
5
4
3
2
1
0
```

### Gambas

`Public Sub Main()Dim siCount As Short For siCount = 10 DownTo 0  Print siCount;;Next End`

Output:

```10 9 8 7 6 5 4 3 2 1 0
```

### GW-BASIC

Works with: PC-BASIC version any
`10 FOR I% = 10 TO 0 STEP -120  PRINT I%30 NEXT I% `

### IS-BASIC

`100 FOR I=10 TO 0 STEP-1110   PRINT I120 NEXT`

### Liberty BASIC

Works with: Just BASIC
Works with: Run BASIC
` for i = 10 to 0 step -1   print inext iend`

### Microsoft Small Basic

` For i = 10 To 0 Step -1  TextWindow.WriteLine(i)EndFor`

### NS-HUBASIC

`10 FOR 1=10 TO 0 STEP -120 PRINT I30 NEXT`

### PureBasic

`For i=10 To 0 Step -1  Debug iNext`

### QB64

CBTJD: 2020/03/14

`FOR n = 10 TO 0 STEP -1    PRINT nNEXT`

### QBASIC

`FOR i = 10 TO 0 STEP -1   PRINT iNEXT i`

### Run BASIC

Works with: Just BASIC
Works with: Liberty BASIC
`for i = 10 to 0 step -1   print inext iend`

### TI-83 BASIC

` :For(I,10,0,-1:Disp I:End `

### TI-89 BASIC

`Local iFor i, 10, 0, –1  Disp iEndFor`

### True BASIC

Works with: QBasic
`FOR i = 10 TO 0 STEP -1    PRINT i; " ";NEXT iPRINTEND`

### Tiny BASIC

`    LET i = 1010  IF i = -1 THEN END	PRINT i    LET i = i - 1    GOTO 10    END`

### Yabasic

Works with: QBasic
`for i = 10 to 0 step -1    print i, " ";next iprintend`

### XBasic

Works with: Windows XBasic
`PROGRAM "downwardfor" DECLARE FUNCTION Entry() FUNCTION Entry()  FOR i% = 10 TO 0 STEP -1    PRINT i%  NEXT i%END FUNCTIONEND PROGRAM`

### ZX Spectrum Basic

`10 FOR l = 10 TO 0 STEP -120 PRINT l30 NEXT l`

## Batch File

`@echo offfor /l %%D in (10,-1,0) do echo %%D`

## bc

`for (i = 10; i >= 0; i--) iquit`

## Befunge

`55+>:.:v@  ^ -1_`

## BQN

Each (`¨`) is an operator in BQN that helps with emulating loops like for and foreach.

`•Show¨⌽↕11`

## Bracmat

`  10:?i& whl'(out\$!i&!i+-1:~<0:?i)`

## Brainf***

`>++++++++[-<++++++>]    //cell 0 now contains 48 the ASCII code for "0"<+.-.                   //print the digits 1 and 0>++++++++++.            //cell 1 now contains the carriage return; print it!>+++++++++              //cell 2 now contains the number 9; this is our counter<<+++++++++>>           //cell 0 now contains 57 the ASCII code for "9"[<<.->.>-]              //print and decrement the display digit; print a newline; decrement the loop variable<<.>.                   //print the final 0 and a final newline`

## Brat

`10.to 0 { n | p n }`

## C

`int i;for(i = 10; i >= 0; --i)  printf("%d\n",i);`

## C#

`for (int i = 10; i >= 0; i--){   Console.WriteLine(i);}`

## C++

`for(int i = 10; i >= 0; --i)  std::cout << i << "\n";`

## Ceylon

`for (i in 10..0) {    print(i);}`

## Chapel

`for i in 1..10 by -1 do	writeln(i);`

In case you wonder why it is not written as 10..1 by -1: by is an operator that works on ranges, and it should work the same when the range was defined earlier, like in

`var r = 1..10;for i in r by -1 do { ... }`

## Clipper

`   FOR i := 10 TO 0 STEP -1      ? i   NEXT`

## Clojure

`(doseq [x (range 10 -1 -1)] (println x))`

## COBOL

free-form

`identification division.program-id. countdown.environment division.data division.working-storage section.01	counter 		pic 99.	88	counter-done	value 0.01	counter-disp	pic Z9.procedure division.	perform with test after varying counter from 10 by -1 until counter-done		move counter to counter-disp		display counter-disp	end-perform	stop run.`
Output:
```10
9
8
7
6
5
4
3
2
1
0```

## CoffeeScript

This could be written either in the array comprehension style, or in "regular" for loop style.

`# The more compact "array comprehension" styleconsole.log i for i in [10..0] # The "regular" for loop style.for i in [10..0]	console.log i # More compact version of the abovefor i in [10..0] then console.log i`
```10
9
8
7
6
5
4
3
2
1
0```

(the output is repeated three times; once for each loop)

## ColdFusion

With tags:

`<cfloop index = "i" from = "10" to = "0" step = "-1">  #i#</cfloop>`

With script:

`<cfscript>  for( i = 10; i <= 0; i-- )  {    writeOutput( i );  }</cfscript>`

## Common Lisp

`(loop for i from 10 downto 1 do  (print i))`

### Using DO

` (do ((n 10 (decf n)))			; Initialize to 0 and downward in every loop    ((< n 0))				; Break condition when negative  (print n))				; On every loop print value `

### Using Tagbody and Go

` (let ((count 10))                ; Create local variable count = 10  (tagbody   dec                           ; Create tag dec    (print count)                ; Prints count    (decf count)                 ; Decreases count    (if (not (< count 0))        ; Ends loop when negative        (go dec))))              ; Loops back to tag dec `

### Using Recursion

` (defun down-to-0 (count)  (print count)  (if (not (zerop count))      (down-to-0 (1- count))))(down-to-0 10) `
Output:
```10
9
8
7
6
5
4
3
2
1
0
```

## Computer/zero Assembly

`LDA 28SUB 29STA 31STA 28BRZ 6 ;branch on zero to STPJMP 0STP...org 28byte 11byte 1byte 0`
Output:

## Crystal

`10.step(to: 0, by: -1).each { |i|    puts i} `

## D

`import std.stdio: writeln; void main() {    for (int i = 10; i >= 0; --i)        writeln(i);    writeln();     foreach_reverse (i ; 0 .. 10 + 1)        writeln(i);}`
Output:
```10
9
8
7
6
5
4
3
2
1
0

10
9
8
7
6
5
4
3
2
1
0```

## dc

does not use GNU extensions

[]s. is a comment

c clears the stack

[~...]p s. to print strings

l<register>x executes the macro

uses the macro f - [p] to print, this can be replaced by any complex expressions.

`c [macro s(swap) - (a b : b a)]s.[Sa Sb La Lb] ss [macro d(2dup) - (a b : a b a b)]s.[Sa d Sb La d Lb lsx] sd [macro m(for) - ]s.[lfx 1 - ldx !<m ] sm 0 10 ldx [p] sf !<mq`

Using it

`|dc < ./for.dc109...0`

See Pascal

## Draco

`proc nonrec main() void:    byte i;    for i from 10 downto 0 do        write(i," ")    odcorp`
Output:
`10 9 8 7 6 5 4 3 2 1 0`

## DWScript

`for i := 10 downto 0 do  PrintLn(i);`

## E

`for i in (0..10).descending() { println(i) }`

## EasyLang

`for i = 10 downto 0  print i.`

## EchoLisp

` (for ((longtemps-je-me-suis-couché-de-bonne-heure (in-range 10 -1 -1)))     (write longtemps-je-me-suis-couché-de-bonne-heure))    → 10 9 8 7 6 5 4 3 2 1 0  `

## EDSAC order code

Including a full routine to print integers in decimal would probably be overkill; at least, it would obscure what is essentially a simple program. We therefore cheat slightly by printing "10\r\n" manually, and using the loop only to print "9\r\n" down to "0\r\n". Note that character codes are stored in the high 5 bits of the 17-bit EDSAC word: so we actually count down from 36,864 to 0 in steps of 4,096.

`[ Loop with downward counter  ==========================   A program for the EDSAC   Prints the integers 10 down to 0   The counter is stored at address [email protected]   Its initial value is 9 * 2^12  (9 in the high 5 bits, representing  the character '9') and it counts  down in steps of 2^12   Works with Initial Orders 2 ]         T56K    [ set load point ]        GK      [ set base address ] [ orders ]         [email protected]    [ print figure shift ]        [email protected]    [ print '1' ]        [email protected]    [ print '0' ]        [email protected]    [ print CR ]        [email protected]    [ print LF ] [ 5 ]   [email protected]    [ print c ]        [email protected]    [ print CR ]        [email protected]    [ print LF ]         [email protected]    [ acc := 0 ]        [email protected]    [ acc += c ]        [email protected]    [ acc -:= character '1' ]        [email protected]    [ c := acc ]         [email protected]     [ branch on non-negative ]         ZF      [ stop ] [ constants ] [ 14 ]  #F      [ πF -- figure shift ][ 15 ]  QF      [ character '1' ][ 16 ]  PF      [ character '0' ][ 17 ]  @F      [ θF -- CR ][ 18 ]  &F      [ ΔF -- LF ] [ variables ] [ 19 ]  P0F     [ used to clear acc ][ 20 ]  OF      [ character c = '9' ]         EZPF    [ start when loaded ]`

## EGL

`for ( i int from 10 to 0 decrement by 1 )   SysLib.writeStdout( i );end`

## Ela

### Standard Approach

`open monad io each [] = do return ()each (x::xs) = do  putStrLn \$ show x  each xs each [10,9..0] ::: IO`

### Alternative Approach

`open monad io countDown m n | n < m = do return ()              | else = do                  putStrLn \$ show n                  countDown m (n - 1) _ = countDown 0 10 ::: IO`

## Elixir

`iex(1)> Enum.each(10..0, fn i -> IO.puts i end)109876543210:ok`

## Erlang

`%% Implemented by Arjun Sunel-module(downward_loop).-export([main/0]). main() ->	for_loop(10).      for_loop(N) -> 	if N > 0 ->		io:format("~p~n",[N] ),		for_loop(N-1);	true ->		io:format("~p~n",[N])	end.	 `
Output:
```10
9
8
7
6
5
4
3
2
1
0
ok```

## ERRE

`    FOR I%=10 TO 0 STEP -1 DO     PRINT(I%)   END FOR `

## Euphoria

`for i = 10 to 0 by -1 do    ? iend for`

## F#

Using an enumerable expression:

`for i in 10..-1..0 do  printfn "%d" i`

Using the 'downto' keyword:

`for i = 10 downto 0 do  printfn "%d" i`

## Factor

`11 <iota> <reversed> [ . ] each`

## FALSE

`10[\$0>][\$." "1-]#.`

## Fantom

` class DownwardFor{  public static Void main ()  {    for (Int i := 10; i >= 0; i--)    {      echo (i)    }  }} `

## FBSL

`#APPTYPE CONSOLE FOR DIM i = 10 DOWNTO 0    PRINT iNEXT PAUSE `

## Fermat

`for i = 10 to 0 by -1 do !!i; od`

## Forth

Unlike the incrementing 10 0 DO-LOOP, this will print eleven numbers. The LOOP words detect crossing the floor of the end limit.

`: loop-down  0 10 do  i .  -1 +loop ;`

## Fortran

Works with: Fortran version 90 and later
`DO i = 10, 0, -1  WRITE(*, *) iEND DO`
Works with: Fortran version 77 and later
`      PROGRAM DOWNWARDFORC Initialize the loop parameters.        INTEGER I, START, FINISH, STEP        PARAMETER (START = 10, FINISH = 0, STEP = -1) C If you were to leave off STEP, it would default to positive one.        DO 10 I = START, FINISH, STEP          WRITE (*,*) I   10   CONTINUE         STOP      END`

## Frink

` for i = 10 to 0 step -1   println[i] `

## GAP

`for i in [10, 9 .. 0] do    Print(i, "\n");od;`

## GML

`for(i = 10; i >= 0; i -= 1)    show_message(string(i))`

## Go

`for i := 10; i >= 0; i-- {  fmt.Println(i)}`
`package main import "fmt"import "time" func main() {	i := 10	for i > 0 {		fmt.Println(i)		time.Sleep(time.Second)		i = i - 1	}	fmt.Println("blast off")}`

## Groovy

`for (i in (10..0)) {    println i}`

## Harbour

`FOR i := 10 TO 0 STEP -1   ? iNEXT`

`import Control.Monad main :: IO ()main = forM_ [10,9 .. 0] print`

## Haxe

Haxe lacks a downward for-loop, but it is easy to create an iterator to serve that purpose.

`class Step {  var end:Int;  var step:Int;  var index:Int;   public inline function new(start:Int, end:Int, step:Int) {    this.index = start;    this.end = end;    this.step = step;  }   public inline function hasNext() return step > 0 ? end >= index : index >= end;  public inline function next() return (index += step) - step;} class Main {  static function main() {    for (i in new Step(10, 0, -1)) {      Sys.print('\$i ');    }  }}`
Output:
`10 9 8 7 6 5 4 3 2 1 0`

## hexiscript

`for let i 10; i >= 0; i--  println iendfor`

## HicEst

`DO i = 10, 0, -1  WRITE() iENDDO`

## HolyC

`I8 i;for (i = 10; i >= 0; --i)  Print("%d\n", i);`

## Icon and Unicon

There are four looping controls 'every', 'repeat', 'until', and 'while' (see Introduction to Icon and Unicon/Looping Controls for more information.) The closest to a 'for' loop is 'every'.

`every i := 10 to 0 by -1 do {   # things to do within the loop   } `

## IDL

Using a loop (with an "increment of minus one" ):

`for i=10,0,-1 do print,i`

But in IDL one would rarely use loops (for anything) since practically everything can be done with vectors/arrays.

The "IDL way of doing things" for the countdown requested in the task would probably be this:

`print,10-indgen(11)`

## Inform 6

`for(i = 10: i >= 0: i--)    print i, "^";`

## Io

`for(i,10,0,-1,    i println)`

## J

J is array-oriented, so there is very little need for loops. For example, one could satisfy this task this way:

```  ,. i. -11
```

J does support loops for those times they can't be avoided (just like many languages support gotos for those time they can't be avoided).

`3 : 0 ] 11  for_i. i. - y do.    smoutput i  end.)`

Though it's rare to see J code like this.

That said, a convenient routine for generating intervals in J might be:

`thru=: <. + [email protected](+*)@-~`

For example:

`   10 thru 010 9 8 7 6 5 4 3 2 1 0`

(or `,.10 thru 0` if you want each number on a line by itself)

This verb "thru" will count up or down, starting and stop at the indicated left and right ending points. (However, note that this particular implementation of 'thru' will return an empty result if the starting and ending values are the same. Whether that's useful or a problem, depends on the application.)

## Java

` for (int i = 10; i >= 0; i--) {    System.out.println(i);} `

## JavaScript

`for (var i=10; i>=0; --i) print(i);`

Alternatively, remaining for the moment within an imperative idiom of JavaScript, in which programs are composed of statements, we could trim the computational costs over longer reversed iterations by moving the mutation into the test, and dropping the third term of a for() statement:

`for (var i = 11; i--;) console.log(i);`

and it sometimes might be more natural, especially at scales at which optimisation becomes an issue, to go one step further and express the same computation with the more economical while statement.

`var i = 11;while (i--) console.log(i);`

In a functional idiom of JavaScript, however, we need an expression with a value (which can be composed within superordinate expressions), rather than a statement, which produces a side-effect but returns no information-bearing value.

If we have grown over-attached to the English morpheme 'for', we might think first of turning to Array.forEach(), and write something like:

`function range(m, n) {  return Array.apply(null, Array(n - m + 1)).map(    function (x, i) {      return m + i;    }  );} range(0, 10).reverse().forEach(  function (x) {    console.log(x);  });`

but this is still a statement with side-effects, rather than a composable expression with a value.

We can get an expression (assuming that the range() function (above) is defined) but replacing Array.forEach with Array.map()

`console.log(  range(0, 10).reverse().map(    function (x) {      return x;    }  ).join('\n'));`

but in this case, we are simply mapping an identity function over the values, so the expression simplifies down to:

`console.log(    range(0, 10).reverse().join('\n'));`

## jq

If range/3 is available in your jq:

`range(10;-1;-1)`

Otherwise:

```range(-10;1) | -.
```

## Julia

`for i in 10:-1:0    println(i)end`

## Kotlin

` // version 1.3.61 fun main() {    (10 downTo 0).forEach { println(it) }} `

## Lambdatalk

` {def downward_for {lambda {:i}   {if {< :i 0}    then (end of loop)    else :i {downward_for {- :i 1}}}}}-> downward_for {downward_for 10}-> 10 9 8 7 6 5 4 3 2 1 0 (end of loop) `

## langur

You can use a for in loop to count downward. You cannot use a for of loop for this.

`for .i in 10..0 {    writeln .i}`
`for .i = 10; .i > -1; .i -= 1 {    writeln .i}`

## Lasso

`loop(-from=10, -to=0, -by=-1) => {^ loop_count + ' ' ^}`

## Lhogho

Slightly different syntax for `for` compared to Logo.

`for "i [10 0] [print :i]`

## Lingo

`repeat with i = 10 down to 0  put iend repeat`

## Lisaac

`10.downto 0 do { i : INTEGER;  i.println; };`

## LiveCode

Livecode's repeat "for" variant does not have a "down to" form, in a function you would need to manually decrement a counter

`local x=10repeat for 10 times                                                                                                     put x & return                                                                                                          add -1 to x                                                                                                           end repeat`

A more idiomatic approach using "with" variant of repeat which does have a "down to" form

`repeat with n=10 down to 1  put nend repeat`

## Logo

If the limit is less than the start, then FOR decrements the control variable. Otherwise, a fourth parameter could be given as a custom increment.

`for [i 10 0] [print :i]`

## Lua

` for i=10,0,-1 do  print(i)end `

## M2000 Interpreter

M2000 can operate a For like in BASIC or Like M2000. In M2000 mode, a For always execute at least one time the block inside. This FOR use absolute value of step, except when we have start value and end value the same value, so from sign of step, interpreter calculate the exit value.

We can change the iterator variable of a For, but this variable is a copy of actual iterator, and next step get the proper value. So we can't change the numbers of steps, but we can use continue to skip rest of code and execute next step, or exit to exit block and stop loop. Also we can use Goto to stop loop and continue from a label.

There is a slower For, the For Next style:

` For i=1 to 10 step 2 : Print i : Next i `

We have to use Exit For to exit from that type of For.

This is not an error (each for has private counter value):

for i=1 to 10 :for i=1 to 2:Print i:Next i:Next i

We get 10 times two values: 1 2

` Form 80, 50Module Checkit {      set switches "+For"      For i=10 to 1 step -1 {            Print i      }      Print i=0      \\ this For switch make it like For in BASIC      \\ block skipped      For i=1 to 10 step -1 {            Print i      }      print i=1      \\ but this is the default behavior      \\      set switches "-For"      \\ sign of step used when start is same as end to calculate the exit value of i      \\ This is the standard, and a For always execute at least one time the block.      \\ use absulute step_Value. Because 10>1 direction is downward.      For i=10 to 1 step -1 {            Print i      }      Print i=0      \\  loop from 1 to 10, using abs(step_value)      For i=1 to 10 step -1 {            Print i      }      print i=11      For i=1 to 1 step -1 {            Print i      }      Print i=0}CheckIt `

## M4

`define(`for',   `ifelse(\$#,0,``\$0'',   `ifelse(eval(\$2 \$3),1,   `pushdef(`\$1',\$2)\$5`'popdef(`\$1')\$0(`\$1',eval(\$2+\$4),\$3,\$4,`\$5')')')')dnl for(`x',`10',`>=0',`-1',`x')`

## Maple

Using an explicit loop:

`for i from 10 to 0 by -1 do print(i) end:`

Pushing the loop into the kernel:

`seq(print(i),i=10..0,-1)`

## Mathematica/Wolfram Language

Mathematica provides several ways to iterate over a range of numbers, small subtle differences are amongst them. 3 possible implementations are (exactly the same output):

Using For:

`For[i = 10, i >= 0, i--, Print[i]]`

Using Do:

`Do[Print[i], {i, 10, 0, -1}]`

Using Scan:

`Scan[Print, Range[10, 0, -1]]`

## MATLAB / Octave

`    for k = 10:-1:0,        printf('%d\n',k)    end; `

A vectorized version of the code is

`  printf('%d\n',10:-1:0);  `

## Maxima

`for i from 10 thru 0 step -1 do print(i);`

## MAXScript

`for i in 10 to 0 by -1 do print i`

## Mercury

`:- module loops_downward_for.:- interface. :- import_module io.:- pred main(io::di, io::uo) is det. :- implementation.:- import_module int. main(!IO) :-   Print = (pred(I::in, !.IO::di, !:IO::uo) is det :-       io.write_int(I, !IO), io.nl(!IO)   ),   int.fold_down(Print, 1, 10, !IO).`

## Metafont

`for i = 10 step -1 until 0: show i; endforend`

The basic set of macros for Metafont defines downto, so that we can write

`for i = 10 downto 0: show i; endfor end`

## min

Works with: min version 0.19.6
`10 :n (n 0 >=) (n puts! n pred @n) while`

Or

`10 (dup 0 <) 'pop (puts pred) () linrec`

## MiniScript

`for i in range(10, 0)    print iend for`

## МК-61/52

`1	0	П0	ИП0	L0	03	С/П`

## Modula-2

`MODULE Downward;  IMPORT InOut;   VAR    i: INTEGER; BEGIN  FOR i := 10 TO 0 BY -1 DO    InOut.WriteInt(i, 2);    InOut.WriteLn  ENDEND Downward.`

## Modula-3

`FOR i := 10 TO 0 BY -1 DO  IO.PutInt(i);END;`

## MUMPS

`LOOPDOWN NEW I FOR I=10:-1:1 WRITE I WRITE:I'=1 ", " KILL I QUIT`

## Nemerle

`for (i = 10; i >= 0; i--) {WriteLine(\$"\$i")}`
`foreach (i in [10, 9 .. 0]) {WriteLine(\$"\$i")}`

## NetRexx

`/* NetRexx */options replace format comments java crossref savelog symbols nobinary   say  say 'Loops/Downward for'   loop i_ = 10 to 0 by -1    say i_.right(2)    end i_ `

## NewLISP

`(for (i 10 0)  (println i))`

## Nim

`for x in countdown(10,0): echo(x)`
Output:
```10
9
8
7
6
5
4
3
2
1
0```

## Oberon-2

`FOR i := 10 TO 0 BY -1 DO  Out.Int(i,0);END;`

## Objeck

` for(i := 10; i >= 0; i--;) {   i->PrintLine();}; `

## OCaml

`for i = 10 downto 0 do  Printf.printf "%d\n" idone`

## Octave

`for i = 10:-1:0  % ...endfor`

## Oforth

`10 0 -1 step: i [ i println ]`

## Oz

`for I in 10..0;~1 do   {Show I}end`

## PARI/GP

`forstep(n=10,0,-1,print(n))`

## Pascal

`for i := 10 downto 0 do  writeln(i);`

## Peloton

English fixed-length opcodes

`<@ ITEFORLITLITLITLIT>0|<@ SAYVALFOR>...</@>|10|-1</@>`

Simplified Chinese variable-length opcodes

`<# 迭代迭代次数字串字串字串字串>0|<# 显示值迭代次数>...</#>|10|-1</#>`

## Perl

`foreach (reverse 0..10) {  print "\$_\n";}`

## Phix

Library: Phix/basics
```for i=10 to 0 by -1 do
?i
end for
```

## PHP

`for (\$i = 10; \$i >= 0; \$i--)  echo "\$i\n";`

or

`foreach (range(10, 0) as \$i)  echo "\$i\n";`

## PicoLisp

`(for (I 10 (ge0 I) (dec I))   (println I) )`

or:

`(mapc println (range 10 0))`

## Pike

`int main(){   for(int i = 10; i >= 0; i--){      write(i + "\n");   }}`

## PL/I

` do i = 10 to 0 by -1;   put skip list (i);end; `

## Plain English

One way might be:

`To run:Start up.Put 11 into a counter.Loop.If the counter is below 0, break.Convert the counter to a string.Write the string on the console.Repeat.Wait for the escape key.Shut down. To decide if a counter is below a number:Subtract 1 from the counter.If the counter is less than the number, say yes.Say no.`

## Pop11

`lvars i;for i from 10 by -1 to 0 do   printf(i, '%p\n');endfor;`

## PowerShell

`for (\$i = 10; \$i -ge 0; \$i--) {    \$i}`

Alternatively, the range operator might be used as well which simply returns a contiguous range of integers:

`10..0`

## Prolog

Although Prolog has a between(Lo,Hi,Value) iterator, there is no built in equivalent for iterating descending values. This is not a show stopper, as it's easy enough to write one.

`rfor(Hi,Lo,Hi) :- Hi >= Lo.rfor(Hi,Lo,Val) :- Hi > Lo, H is Hi - 1, !, rfor(H,Lo,Val). reverse_iter :-  rfor(10,0,Val), write(Val), nl, fail.reverse_iter.`
```?- reverse_iter.
10
9
8
7
6
5
4
3
2
1
0
true.
```

## Python

`for i in xrange(10, -1, -1):    print i`

### List comprehension

`[i for i in xrange(10, -1, -1)]`
`import pprintpprint.pprint([i for i in xrange(10, -1, -1)]) `

## Quackery

`11 times [ i echo sp ]`
Output:
`10 9 8 7 6 5 4 3 2 1 0`

## R

`for(i in 10:0) {print(i)}`

## Racket

` #lang racket (for ([i (in-range 10 -1 -1)])  (displayln i)) `

## Raku

(formerly Perl 6)

Works with: Rakudo Star version 2010.08
`for 10 ... 0 {    .say;}`

## REBOL

`for i 10 0 -1 [print i]`

## Retro

`11 [ putn space ] iterd`

## REXX

### version 1

(equivalent to version 2 and version 3)

`  do j=10  to 0  by -1  say j  end`

### version 2

(equivalent to version 1 and version 3)

`  do j=10  by -1  to 0  say j  end`

### version 3

(equivalent to version 1 and version 2)

Anybody who programs like this should be hunted down and shot like dogs!

Hurrumph! Hurrumph!

`  do j=10  by -2  to 0  say j  j=j+1     /*this increments the  DO  index.   Do NOT program like this! */  end`

### version 4

This example isn't compliant to the task, but it shows that the increment/decrement can be a non-integer:

`  do j=30  to 1  by -.25  say j  end`

## Ring

count from 10 to 0 by -1 step:

` for i = 10 to 0 step -1 see i + nl next `

## Ruby

`10.downto(0) do |i|   puts iend`

## Rust

`fn main() {    for i in (0..=10).rev() {        println!("{}", i);    }}`

## Salmon

`for (x; 10; x >= 0; -1)    x!;`

## Sather

`class MAIN is  main is    i:INT;    loop i := 10.downto!(0);       #OUT  + i + "\n";    end;  end;end;`

## Scala

`for(i <- 10 to 0 by -1) println(i)//or10 to 0 by -1 foreach println`

## Scheme

`(do ((i 10 (- i 1)))    ((< i 0))    (display i)    (newline))`

## Scilab

Works with: Scilab version 5.5.1
`for i=10:-1:0    printf("%d\n",i)end`
Output:
```10
9
8
7
6
5
4
3
2
1
0
```

## Seed7

`for i range 10 downto 0 do  writeln(i);end for;`

## Sidef

for(;;) loop:

`for (var i = 10; i >= 0; i--) {    say i}`

for-in loop:

`for i in (11 ^.. 0) {    say i}`

.each method:

`10.downto(0).each { |i|    say i}`

## Simula

`BEGIN    Integer i;    for i := 10 step -1 until 0 do    BEGIN        OutInt(i, 2);        OutImage    ENDEND`

## Slate

`10 downTo: 0 do: [| :n | print: n]`

## Smalltalk

`10 to: 0 by: -1 do:[:aNumber |   aNumber displayNl.]. 10 downTo: 0 do:[:eachNumber |   eachNumber displayNl.]`

Both enumerate 10 to 0 inclusive.

Non-Smalltalkers might be confused when seeing:

`(10 to: 0 by: -1) do:[:eachNumber |   eachNumber displayNl.]`

which has the same effect, but a slightly different mechanism.

The first one sends a "to:by:do:" message to the Integer 10, passing "0", "-1", and the closure as arguments. There (in the integer), the counting and closure invokation takes place (who cares how it does it?).

The second example first instantiates a range-collection object (called Interval in Smalltalk) with the "to:by:" message (sent to the integer), and then this Interval object gets a "do:" message.
Which - like all collections - enumerates its elements, in this case [10..0].

Thus the first variant is one message send (aka virtual function call) to the number, whereas the second is two message sends and an object instantiation.

The nice thing with Intervals is that they can be concatenated with a "," operator (like all collections); thus, I could also write:

`(10 to: 5 by: -1),(0 to: 4) do:[:eachNumber |   eachNumber displayNl.]`

to enumerate in a different order,
or combine ranges with a constant array:

`(10 to: 0 by: -2),#(99 999),(1 to: 9 by: 2) do:[:each |   each displayNl.]`

or with a computed array:

`(10 to: 0 by: -2),{ 10 factorial . 11 factorial},(1 to: 9 by: 2) do:[:each |   each displayNl.]`

PS: there is also a reverse do, as in:

`(0 to:10) reverseDo:[:each |   each displayNl.]`

## SNOBOL4

`        COUNT = 10LOOP    OUTPUT = COUNT        COUNT = COUNT - 1        GE(COUNT, 0)     :S(LOOP)END`

## SNUSP

`++++++++++>++++++++++!/- @!\[email protected]\[email protected]@@[email protected]#   atoi    \n      counter  #\?>.</  \ @@@[email protected]+++++#   itoa                       loop`

## Sparkling

`for var i = 10; i >= 0; i-- {    print(i);}`

## Spin

Works with: BST/BSTC
Works with: FastSpin/FlexSpin
Works with: HomeSpun
Works with: OpenSpin
`con  _clkmode = xtal1 + pll16x  _clkfreq = 80_000_000 obj  ser : "FullDuplexSerial.spin" pub main | n  ser.start(31, 30, 0, 115200)   repeat n from 10 to 0    ser.dec(n)    ser.tx(32)   waitcnt(_clkfreq + cnt)  ser.stop  cogstop(0)`
Output:
`10 9 8 7 6 5 4 3 2 1 0`

## SPL

`> i, 10..0,-1  #.output(i)<`

## SSEM

The SSEM can't print, so the results are stored in an array at addresses 22 to 31. Array access is done using self-modifying code: on each iteration we subtract the current value of n (stored at address 18) from the illegal instruction c to 32, yielding the actual instruction we use to store n into the array.

`10001000000000100000000000000000   0. -17 to c11001000000001100000000000000000   1. c to 1911001000000000100000000000000000   2. -19 to c01001000000000010000000000000000   3. Sub. 1800010000000001100000000000000000   4. c to 801001000000000100000000000000000   5. -18 to c11001000000001100000000000000000   6. c to 1911001000000000100000000000000000   7. -19 to c00000000000000000000000000000000   8. generated at run time11110000000000010000000000000000   9. Sub. 1501001000000001100000000000000000  10. c to 1811110000000000010000000000000000  11. Sub. 1500000000000000110000000000000000  12. Test00001000000000000000000000000000  13. 16 to CI00000000000001110000000000000000  14. Stop10000000000000000000000000000000  15. 111111111111111111111111111111111  16. -100000100000001100000000000000000  17. c to 3201010000000000000000000000000000  18. 10`

## Stata

See forvalues and foreach in Stata help.

`forvalues n=10(-1)0 {        display `n'} forvalues n=10 9 to 0 {        display `n'} foreach n of numlist 10/0 {        display `n'}`

## Swift

`for i in stride(from: 10, through: 0, by: -1) {  println(i)}`

Alternately:

`for i in lazy(0...10).reverse() {  println(i)}`

In Swift 1.2 Alternately:

`for i in reverse(0 ... 10) {  println(i)}`

Alternately (removed in Swift 3):

`for var i = 10; i >= 0; i-- {  println(i)}`

Swift 3:

`for i in (0...10).reversed() {    print(i)}`

## Tailspin

Not really a for-loop, but it sends a stream of values where each gets treated the same way.

` 10..0:-1 -> '\$;' -> !OUT::write `

## Tcl

`for {set i 10} {\$i >= 0} {incr i -1} {    puts \$i}# puts "We have liftoff!"`

## Trith

`10 inc iota reverse [print] each`
`10 [dup print dec] [dup 0 >=] while drop`

## TUSCRIPT

` \$\$ MODE TUSCRIPTLOOP n=10,0,-1 PRINT nENDLOOP `

## UNIX Shell

Works with: Bourne Shell
`i=10while test \$i -ge 0; do	echo \$i	i=`expr \$i - 1`done # or jot - 10 0 -1 # or seq 10 -1 0`

Works with: bash
`for(( Z=10; Z>=0; Z-- )); do    echo \$Zdone #or for Z in {10..0}; do    echo \$Zdone `

## UnixPipes

Works with: OpenBSD version 4.9
`yes '' | cat -n | head -n 11 | while read n; do	expr \$n - 1done | tail -r`

This pipe uses several nonstandard commands: `cat -n` and `tail -r` might not work with some systems. If there is no `tail -r`, try `tac`.

## Ursa

`decl int ifor (set i 10) (> i -1) (dec i)	out i endl consoleend for`

## V

`10 [0 >]  [dup puts pred]while`

## Vala

`for (int i = 10; i >= 0; --i)    stdout.printf("%d\n", i);`

## VBA

`For i = 10 To 0 Step -1   Debug.Print iNext i`

## Vedit macro language

`for (#1 = 10; #1 >= 0; #1--) {    Num_Type(#1)}`

## Verilog

` module main;  integer  i;   initial begin     for(i = 10; i >= 0; i = i - 1)  \$write(i);  \$finish ;  endendmodule `

## Visual Basic .NET

`For i = 10 To 0 Step -1    Console.WriteLine(i)Next`

## Vlang

`fn main() {    for i := 10; i >= 0; i-- {        print('\$i ')    }}`
Output:
```10 9 8 7 6 5 4 3 2 1 0
```

## Wart

`for i 10 (i >= 0) --i  prn i`

## Wren

`for (i in 10..0) System.write("%(i) ")System.print()`
Output:
```10 9 8 7 6 5 4 3 2 1 0
```

## XPL0

`include c:\cxpl\codes;          \intrinsic 'code' declarationsint I;for I:= 10 downto 0 do        [IntOut(0, I); CrLf(0)]`

## Z80 Assembly

Because of the way looping typically works in hardware, as well as 10 being two digits, it's more efficient to only print numbers 9 through 1 in the loop body, and do the rest outside it.

`org &1000 LD A,'1'CALL &BB5ALD A,'0'CALL &BB5A LD B,9LD A,'9' for:CALL &BB5ADEC ADJNZ for LD A,'0'JP &BB5A	;its RET returns to BASIC for us.`
Output:
```Amstrad Microcomputer   (v4)
and Locomotive Software Ltd.

BASIC 1.1
`foreach n in ([10..0,-1]){ println(n) }[10..0,-1].apply() //-->L(10,9,8,7,6,5,4,3,2,1,0)   // tail recursionfcn(n){ n.println(); if(n==0)return(); return(self.fcn(n-1)) }(10)`
`const std = @import("std"); pub fn main() !void {    var i: u8 = 11;    while (i > 0) {        i -= 1;        try std.io.getStdOut().writer().print("{d}\n", .{i});    }}`