Crate type_val [] [src]

This crate allows for the creation of type-level values. Any value can be type-level as long as it can be initialized as a constant. All type-level values implement the TypeVal trait, and so can be provided as type parameters.


extern crate type_val;
use type_val::TypeVal;

use std::marker::PhantomData;

fn main() {
    let mut adder = Adder::<Two, One>::new();
    assert_eq!(adder.sum, 2);
    assert_eq!(adder.sum, 3);
def_type_val! {
    type One: u32 = 1;
    type Two: u32 = 2;
struct Adder<S, I> {
    sum: u32,
    _marker: PhantomData<(S, I)>,
impl <S, I> Adder<S, I>
    where S: TypeVal<u32>,
          I: TypeVal<u32>,
    fn new() -> Adder<S, I> {
        Adder {
            // Get the value of S
            sum: S::VAL,
            _marker: PhantomData,
    fn add(&mut self) {
        // Get the value of I
        self.sum += I::VAL;



This macro is used to implement the TypeVal trait. Any number of values can be initialized with a single invocation. Items prefixed by pub are public. Attributes to be applied to items in a block, including doc comments, should go above their targets.



A trait implemented by type-level values.