code.rs

#[derive(Clone, Copy)]
struct Op(fn(u16, u16));

// lets you call foo() instead of foo.0() (where foo: Op)
impl std::ops::Deref for Op {
    type Target = fn(u16, u16);
    fn deref(&self) -> &fn(u16, u16) { &self.0 }
}

fn op_mov(one: u16, two: u16) {
}

fn op_add(one: u16, two: u16) {
}

fn op_nand(one: u16, two: u16) {
}

fn op_shl(one: u16, two: u16) {
}

fn op_shr(one: u16, two: u16) {
}

fn op_jz(one: u16, two: u16) {
}

fn op_lt(one: u16, two: u16) {
}

fn op_gt(one: u16, two: u16) {
}

fn op_in(one: u16, two: u16) {
}

fn op_out(one: u16, two: u16) {
}

fn main() {
    let methods: std::collections::HashMap<u16, Op> =
        [(0b0000, Op(op_mov)),
         (0b0001, Op(op_add)),
         (0b0010, Op(op_nand)),
         (0b0011, Op(op_shl)),
         (0b0100, Op(op_shr)),
         (0b0101, Op(op_jz)),
         (0b0110, Op(op_lt)),
         (0b0111, Op(op_gt)),
         // No 0b1000-0b1101.
         (0b1110, Op(op_in)),
         (0b1111, Op(op_out))].iter().cloned().collect();

    methods.get(&0b0000);
}