Functions and flow

Functions

Parameters and public results have explicit types. Use an expression body for a single result, or a block with return for several steps.

pub fun square(value: Int) -> Int = value * value

pub fun label(value: Int) -> Text:
    if value > 0:
        return "positive"
    elif value == 0:
        return "zero"
    else:
        return "negative"

A block without a result arrow returns Unit. Parameters are immutable. Default arguments, named arguments, and Kalm overload declarations are deferred.

Loops

for accepts an array or Iterable. Its loop binding is immutable. while repeats while a Boolean condition holds. stop exits a loop; next skips to the next iteration.

pub fun printNumbers() -> Unit:
    for value in range(3):
        sayLine(value)

Matching

choose returns the result of a matching when branch. Match every variant of a choice or every permitted type of a closed hierarchy; _ is a catch-all.

See matching examples and types and contracts.

Lambdas

Lambdas receive their parameter types from a Kalm or Java single-method contract. Use fun value => expression, or a braced body with return.

pub fun loud() -> java.util.function.Function<Text, Text>:
    return fun name => name.toUpperCase()

For exceptions and cleanup, continue with resources.