Pass functions as parameters to other functions

[dark64]

Abstract

A feature that could be of great benefit to us is the ability to pass functions as parameters. This would allow us to neatly do a Merkle tree implementations by passing down a hash function.

Motivation

As we use a type-first syntax eg. field f, we cannot leverage the Rust way of doing this f: fn(i32) -> i32.
A possible workaround that fits the current syntax would be to define a custom type that represents a function signature:

type sumf = (field, field) -> field

def sum(field a, field b) -> field:
    return a + b

def foo(field a, field b, sumf s) -> field:
    return s(a, b)

def main() -> field:
    return foo(2, 2, sum)

This issue is still open for discussion and is subject to change.

Specification

TBA

Backwards Compatibility

No incompatibilities for now.