Functions

Functions abstract statements into reusable blocks. There are two types of functions - pure functions and finish functions.

No function type may be used in a way that would cause recursion.

Pure Functions

function count_valid(v count) bool {
    return v >= 0
}

Pure functions can contain data processing statements (let, if, match, etc.), must have a return type, and must return a value with return.

Pure functions are valid in any expression (see also Functions in the Expressions section). But due to the restrictions on finish blocks and functions, they may only be used in actions, pure functions, command seal/open/policy/recall blocks outside finish blocks, and global let definitions (subject to their restrictions).

Finish Functions

finish function set_foo(device id, new int) {
    update FooCounter[device: device]=>{count: current} to {count: new}
}

Finish functions allow the abstraction of statements used in finish blocks. Thus, they can only contain finish block statements (create, update, delete, emit) and cannot return a value. Finish functions are called like regular functions, except they stand alone.

// In a policy block:
let new = this.current + 1
finish {
    set_foo(this.device_id, new)
}

Finish functions can call other finish functions in the same way as in finish blocks. Like finish blocks, expressions in finish functions are limited to named values and constants.