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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 }

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)

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") }

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!")