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Structure
Loops

Perform an action multiple times based on a boolean condition, checked before the first action (WHILE .. DO)

Starting with a variable x=1, Print the sequence "1,2,4,8,16,32,64,128," by doubling x and checking that x is less than 150.
ruby
x=1
while x < 150
puts x
x *=2
end
java
int x = 1;
while (x < 150) {
System.out.println(x+",");
x*=2;
}
perl
my $x = 1;
while($x < 150) {
print $x, ",";
$x *=2
}
groovy
x = 1
while (x < 150) {
print x + ","
x *= 2
}
println()
scala
var x = 1 ; while (x < 150) { printf("%d,", x) ; x *= 2 }
python
x = 1
while x < 150:
print '%s, ' % x,
x *= 2
cpp
int x = 1;

while (x < 150) { x *= 2; Console::Write("{0},", x); }
Console::WriteLine();
for (int x = 1; x < 150; x *= 2) { std::cout << x << ","; }
std::cout << std::endl;
fsharp
let mutable x = 1
while x < 150 do printf "%d, " x ; (x <- x * 2) done
erlang
X = 1, print_while_X_less_150(X).
Pred = fun (X) -> X < 150 end,
Action = fun (X) -> io:format("~B,", [X]), X * 2 end,
X = 1,

while_do(Pred, Action, X).
php
$x = 1;
while($x < 150) {
echo "$x,";
$x *= 2;
}
$x = 0;
$c = pow(2, $x);
while($c < 150) {
echo "$c,";
$c = pow(2, $x++);
}

Perform an action multiple times based on a boolean condition, checked after the first action (DO .. WHILE)

Simulate rolling a die until you get a six. Produce random numbers, printing them until a six is rolled. An example output might be "4,2,1,2,6"
ruby
# Ruby has no DO..WHILE construct. Need to write it as a WHILE
rnd = 0
while (rnd != 6)
rnd = rand(6)+1
print rnd
print "," if (rnd!=6)
end
java
int rnd;
do {
rnd = (int)(Math.random()*6)+1;
System.out.print(rnd);
if (rnd!=6) {
System.out.print(",");
}
} while(rnd!=6);
perl
do {
my $number = int(rand(6)+1);
print $number;
print ',' if ($number != 6);
} while ($number != 6);
groovy
// Groovy has no do..while; use a normal while
int dice = 0
while (dice != 6) {
dice = Math.random() * 6 + 1
print dice
if (dice != 6) print ','
}
scala
val dice = new GenRandInt(1, 6) ; var rnd = 0 ; var fmt = ""
do { rnd = dice.next ; fmt = if (rnd != 6) "%d," else "%d" ; printf(fmt, rnd) } while (rnd != 6)
python
import random, itertools

def dice():
while True:
yield random.randint(1,6)

print ", ".join(str(d) for d in itertools.takewhile(lambda x: x < 6, dice()))
cpp
Random^ rnd = gcnew Random;

int dice = rnd->Next(1, 7); Console::Write("{0}", dice);
do { Console::Write(",{0}", (dice = rnd->Next(1, 7))); } while (dice != 6);
Console::WriteLine();
fsharp
open System
let rand = Random()

Seq.initInfinite (fun _ -> rand.Next(1, 7))
|> Seq.takeWhile (fun x -> x < 6)
|> fun items -> String.Join(",", items)
|> function s when s = "" -> printfn "6" | s -> printfn "%s,6" s
erlang
Pred = fun (DiceRoll) -> DiceRoll =/= 6 end,
Action = fun (DiceRoll) -> io:format("~B,", [DiceRoll]), dice_roll() end,

do_while(Pred, Action, dice_roll()).
-module(dice).
-export([start/0]).

start() ->
roll(dice_roll()).

roll(6) ->
io:format("6~n", []);
roll(N) ->
io:format("~B,", [N]),
roll(dice_roll()).

dice_roll() -> random:uniform(6).
php
do {
$rand = rand(1,6);
echo $rand;
if ($rand != 6) echo ", ";
} while ($rand != 6);

Perform an action a fixed number of times (FOR)

Display the string "Hello" five times like "HelloHelloHelloHelloHello"
ruby
puts "Hello"*5
5.times { print "Hello" }
java
for(int i=0;i<5;i++) {
System.out.print("Hello");
}
perl
print "Hello" x 5
print "Hello" for (1..5)
groovy
println "Hello" * 5
5.times { print "Hello" }; println()
scala
// Using overloaded '*' operator (String-specific)
print("Hello" * 5)
List.range(0, 5) foreach { (_) => print("Hello") }
for (_ <- List.range(0, 5)) print("Hello")
// Lazy version
for (_ <- Stream.range(0, 5)) print("Hello")
dotimes(5, _ => print("Hello"))
(0 until 5) foreach { (_) => print("Hello") }
5 times { print("Hello") }
python
print "Hello" * 5
cpp
for(int i = 0; i < 5; ++i) Console::Write("Hello");
for(int i = 5; i > 0; --i) Console::Write("Hello");
dotimes(5, hello);
fsharp
for i = 1 to 5 do printf "Hello" done
dotimes 5 (fun () -> printf "Hello")
// Repetition via ranging over a List type(index ignored)
for _ in list do printf "Hello" done
// Repetition via ranging over a Sequence type(index ignored)
for _ in sequence do printf "Hello" done
// Repetition via ranging over an Array type(index ignored)
for _ in array do printf "Hello" done
erlang
dotimes(5, fun () -> io:format("Hello") end).
lists:foreach(fun (_) -> io:format("Hello") end, lists:seq(1, 5)).
ocaml
let rec write_hello = function
0 -> ()
| 1 ->
print_string "Hello" ;
write_hello (n-1)
;;
write_hello 5;;
php
for($i = 0; $i < 5; $i++) {
echo "Hello";
}

Perform an action a fixed number of times with a counter

Display the string "10 .. 9 .. 8 .. 7 .. 6 .. 5 .. 4 .. 3 .. 2 .. 1 .. Liftoff!"
ruby
10.downto(1) { |n| print n, " .. " }
puts "Liftoff!"
java
for(int i=10; i>=1; i--) {
System.out.print(i + " .. ");
}
System.out.print("Liftoff!");
perl
for (my $i = 10; $i > 0; $i--) {
print "$i .. ";
}
print "Liftoff!";
groovy
10.downto(1) { print it + " .. " }
println "Liftoff!"
scala
for (i <- List.range(1, 11).reverse) printf("%d .. ", i) ; println("Liftoff!")
for (i <- List.range(-10, 0)) printf("%d .. ", (-i)) ; println("Liftoff!")
var i = 10 ; while (i > 0) { printf("%d .. ", i) ; i -= 1 } ; println("Liftoff!")
for (i <- -10 to -1) printf("%d .. ", (-i)) ; println("Liftoff!")
python
print " .. ".join(str(i) for i in range(10, 0, -1)), ".. liftoff!"
cpp
for(int i = 10; i != 0; --i) Console::Write("{0} .. ", i);
Console::WriteLine("Liftoff!");
fsharp
for i = 10 downto 1 do printf "%d .. " i done
printfn "Liftoff!"
// Repetition via ranging over a Sequence type
for i in {10 .. -1 .. 1} do printf "%d .. " i done ; printfn "Liftoff!"
erlang
fromto(10, 1, -1, fun (X) -> io:format("~B .. ", [X]) end), io:format("Liftoff!~n").
lists:foreach(fun (X) -> io:format("~B .. ", [X]) end, lists:seq(10, 1, -1)), io:format("Liftoff!~n").
php
for($i = 10; $i > 0; $i--) {
echo $i." .. ";
}
echo "Liftoff!";