Loops/Downward for

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Task
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.

Contents

[edit] 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 Accumulator
Send 		= 	$9000		;routine not implemented here
PrintNewLine	=	$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 digits
PrintTwoDigits
		PHA 
		LSR 
		LSR 
		LSR 
		LSR 
		JSR     PrintDigit
		PLA 
		AND     #$0F
		JSR     PrintDigit
		RTS 
 
;Convert value in Accumulator to an Ascii hex digit
PrintDigit
		ORA	#$30
		JSR	Send		;routine not implemented here
		RTS

[edit] Ada

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

[edit] 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

[edit] AmigaE

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

[edit] AutoHotkey

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

[edit] AWK

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

[edit] BASIC

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

[edit] BBC BASIC

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

[edit] bc

for (i = 10; i >= 0; i--) i
quit

[edit] Befunge

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

[edit] Bracmat

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

[edit] Brat

10.to 0 { n | p n }

[edit] C

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

[edit] C++

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

[edit] C#

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

[edit] Clojure

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

[edit] CoffeeScript

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

# The more compact "array comprehension" style
console.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 above
for 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)

[edit] 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>

[edit] Common Lisp

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

[edit] 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

[edit] 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 !<m
q

Using it 

|dc < ./for.dc
10
9
...
0

[edit] Delphi

See Pascal

[edit] DWScript

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

[edit] E

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

[edit] EGL

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

[edit] 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

[edit] Euphoria

for i = 10 to 0 by -1 do
    ? i
end for

[edit] Ela

[edit] Standard Approach

open console imperative
 
each writen [10,9..0]

Function 'each' is defined in imperative module as: 

 
each f (x::xs) = f x $ each f xs
each _ []      = ()

[edit] Alternative Approach

open console
 
countDown m n | n < m = ()
              | else = writen n $ countDown m (n-1)
 
countDown 0 10

[edit] Factor

11 iota <reversed> [ . ] each

[edit] FALSE

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

[edit] Fantom

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

[edit] 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 ;

[edit] Fortran

Works with: Fortran version 90 and later
DO i = 10, 0, -1
  WRITE(*, *) i
END DO
Works with: Fortran version 77 and later
      PROGRAM DOWNWARDFOR
C 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

[edit] F#

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

[edit] GML

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

[edit] Go

for i := 10; i >= 0; i-- {
  fmt.Println(i)
}

[edit] Groovy

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

[edit] Haskell

import Control.Monad
forM_ [10,9..0] print

[edit] HicEst

DO i = 10, 0, -1
  WRITE() i
ENDDO

[edit] 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)

[edit] 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
   }
 

[edit] Inform 6

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

[edit] 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.
            i 1!:2 ]2 
        end.
     i.0 0
   )

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

[edit] Java

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

[edit] JavaScript

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

[edit] Liberty BASIC

 
for i = 10 to 0 step -1
   print i
next i
end
 

[edit] Lisaac

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

[edit]

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]

[edit] Lua

 
for i=10,0,-1 do
  print(i)
end
 

[edit] 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
')

[edit] 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)

[edit] Mathematica

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]]

[edit] 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);

[edit] Maxima

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

[edit] MAXScript

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

[edit] 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).

[edit] Metafont

for i = 10 step -1 until 0: show i; endfor
end

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

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

[edit] МК-61/52

1	0	П0	ИП0	L0	03	С/П

[edit] Modula-2

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

[edit] Modula-3

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

[edit] MUMPS

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


[edit] Nemerle

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

[edit] 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_
 

[edit] Oberon-2

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

[edit] Objeck

 
for(i := 10; i >= 0; i -= 1;) {
   i->PrintLine();
};
 

[edit] OCaml

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

[edit] Octave

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

[edit] Oz

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

[edit] PARI/GP

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

[edit] Pascal

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

[edit] Perl

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

[edit] Perl 6

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

[edit] PHP

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

or 

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

[edit] PicoLisp

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

or: 

(mapc println (range 10 0))

[edit] Pike

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

[edit] PL/I

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

[edit] Pop11

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

[edit] 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

[edit] PureBasic

For i=10 To 0 Step -1
  Debug i
Next

[edit] Python

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

[edit] R

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

[edit] Racket

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

[edit] REBOL

for i 10 0 -1 [print i]

[edit] Retro

11 [ putn space ] iterd

[edit] REXX

[edit] version 1

(equivalent to version 2 and version 3) 

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

[edit] version 2

(equivalent to version 1 and version 3) 

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

[edit] 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

[edit] 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

[edit] Ruby

10.downto(0) do |i|
   puts i
end

[edit] Salmon

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

[edit] Sather

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

[edit] Scala

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

[edit] Scheme

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

[edit] Seed7

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

[edit] Slate

10 downTo: 1 do: [| :n | print: n]

[edit] Smalltalk

10 to: 1 by: -1 do:[:aNumber | 
  aNumber display.
  Character space display.
]

[edit] SNUSP

++++++++++>++++++++++!/- @!\=@\.@@@-@-----#   atoi
    \n      counter  #\?>.</  \ @@@+@+++++#   itoa
                       loop

[edit] Tcl

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

[edit] TI-83 BASIC

 
:For(I,10,0,–1)
  :Disp I
:End
 

[edit] TI-89 BASIC

Local i
For i, 10, 0, –1
  Disp i
EndFor

[edit] Trith

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

[edit] TUSCRIPT

 
$$ MODE TUSCRIPT
LOOP n=10,0,-1
 PRINT n
ENDLOOP
 

[edit] UnixPipes

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

[edit] UNIX Shell

Works with: Bourne Shell
i=10
while test $i -ge 0; do
	echo $i
	i=`expr $i - 1`
done
Works with: bash
for(( Z=10; Z>=0; Z-- )); do
    echo $Z
done
Works with: Bourne Shell
Library: jot
for i in `jot - 10 0 -1`; do
	echo $i
done
Works with: Bourne Shell
for i in `seq 10 -1 0`; do
	echo $i
done
 
# or better yet
seq 10 -1 0
 

[edit] V

10 
[0 >]
  [dup puts pred]
while

[edit] Vedit macro language

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

[edit] Visual Basic .NET

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

[edit] XPL0

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

[edit] ZX Spectrum Basic

10 FOR l = 10 TO 0 STEP -1
20 PRINT l
30 NEXT l
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