Capy-Bearer Documentation

A function can be stored in a variable, passed to another function and returned from one. The type is written as the parameter list and result, with no name.

function double(value : s32) s32 { -> value * 2 }

function apply(value : s32, transform : function(value : s32) s32) s32 {
    -> transform(value)
}

function RENDER(request : dval) {
    print(apply(21, double), "\n")
}

Closures

A lambda written inline captures the locals it reads:

function RENDER(request : dval) {
    var offset := 10
    var shift := function(value : s32) s32 { -> value + offset }
    print(shift(5), "\n")
}

A captured managed value — a string, array or dval — stays alive as long as the closure does. Captures are by value: reassigning offset after building the closure does not change what the closure sees.

Where they are used

The collection helpers take function values: map, filter, each, find, some, every and sort all accept a callback whose signature the compiler checks at the call site. That check is why map over an array and map over a dval are separate overloads — the callbacks differ.