KATASCRIPT / PLAYGROUND

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func make_counter(start: Int, step: Int): Func {
    let value = start
    ret func(): Int {
        value = value + step
        ret value
    }
}
let next = make_counter(0, 1)
let tens = make_counter(0, 10)
print("next: {next()}")
print("next: {next()}")
print("tens: {tens()}")
print("next: {next()}")
print("tens: {tens()}")

Execution stays in this browser. Click a line number to set a breakpoint. Debug pauses before a statement; Step follows execution into user functions. Each checkpoint is reconstructed by deterministic replay. Execution limits and debugger behavior →