Functions¶

Keel functions use the following syntax:

fn name(arg1, arg2, ..., argN) {
    // put the function's code here
}

Function arguments can be typed by using this syntax: arg: type. For example:

fn condition(elem1, elem2, flag: bool) {
    return if flag {elem1} else {elem2};
}

Functions are called with name(arg1, arg2, ..., argN). A function can also not take any arguments as input.

Functions can be defined at the toplevel or inside other functions.

The main function is special. It doesn't take any arguments, and any Keel file used as the program's entry point must define a main function.

Keel supports function polymorphism (and does compile-time monomorphization), meaning that a single function can operate on arguments of different types. For example:

fn add(x, y) {
    return x+y;
}

fn main() {
    let result = add(1, 1);
    let result2 = add(1.5, 1.5);
    let result3 = add("Hello", ", world!");
    let result4 = add([0,1], [2,3]);
}

Inline functions¶

Inline functions can be declared anywhere an expression is expected (see in Data types). The syntax is the same as a normal function declaration, just without the name.

fn main() {
    let my_func = fn(n: int) {return if n <= 1 {n} else {10};};
    print(my_func(5));
}