langref.org - scala, erlang, and csharp - Structure

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.

scala

var x = 1 ; while (x < 150) { printf("%d,", x) ; x *= 2 }

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).

csharp

int x = 1;

while (x < 150)
{
x *= 2;
Console.Write("{0},", 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"

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)

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).

csharp

System.Random die = new System.Random();
int roll;

do
{
roll = die.Next(1, 6);
Console.Write(roll);
if (roll < 6) Console.Write(",");
}
while (roll != 6);

Perform an action a fixed number of times (FOR)

Display the string "Hello" five times like "HelloHelloHelloHelloHello"

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") }

erlang

dotimes(5, fun () -> io:format("Hello") end).

lists:foreach(fun (_) -> io:format("Hello") end, lists:seq(1, 5)).

csharp

string text = "Hello";

for (int i = 0; i < 5; i++)
{
Console.Write(text);
}

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!"

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!")

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").

csharp

for (int i = 10; i > 0; i--)
{
Console.Write("{0} .. ", i);
}

Console.WriteLine("Liftoff!");