Control flow

Loops

While Loop

int i = 1
while (i <= 5) {
    term.println(i.str())
    i = i + 1
}

An infinite loop is while (true) { ... } — exit it with break or return.

For Loops

for iterates an integer range (start .. end, end exclusive) or the elements of an array:

# Range: prints 0 1 2 3 4
for i in 0..5 {
    term.println(i.str())
}

# The bounds are ordinary expressions, evaluated once:
for i in 1..n + 1 {
    fact = fact * i
}

# Array iteration binds each element in turn:
array[str] names = new array[str]{"ada", "bob", "cid"}
for name in names {
    term.println(name)
}

A range only counts upward, and there is no step: for i in 5..0 runs zero times rather than counting down. To iterate in reverse or by a step other than 1, use a while loop with your own counter.

break and continue

break leaves the innermost loop; continue skips to the next iteration (in a for, the increment still runs):

int sum = 0
for i in 0..100 {
    if (i >= 10) { break; }       # stop once i reaches 10
    if (i % 2 == 0) { continue; } # skip even numbers
    sum = sum + i
}  # sum = 1+3+5+7+9 = 25

The loop variable is fresh each iteration

A for loop's variable is a new binding on every iteration, so a closure created in the body captures that iteration's value (the same rule as let in JavaScript, or for in Kotlin/Swift):

array[func[int]] handlers = new array[func[int]](3)
for i in 0..3 {
    handlers[i] = func() int { return i; }
}
term.println(handlers[0]().str())  # 0
term.println(handlers[1]().str())  # 1  (not 2!)
term.println(handlers[2]().str())  # 2

A while loop has no loop variable — its counter is an ordinary variable you declare outside, so it is shared across iterations. To capture per iteration, bind a fresh local inside the body:

int j = 0
while (j < 3) {
    int cur = j  # fresh each iteration
    handlers[j] = func() int { return cur; }  # captures 0, 1, 2
    j = j + 1
}