typenum - Rust
Description: This crate provides type-level numbers evaluated at compile time. It depends only on libcore.
Keywords: rust, rustlang, rust-lang, typenum

# Crate typenum

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This crate provides type-level numbers evaluated at compile time. It depends only on libcore.

The traits defined or used in this crate are used in a typical manner. They can be divided into two categories: marker traits and type operators.

Many of the marker traits have functions defined, but they all do essentially the same thing: convert a type into its runtime counterpart, and are really just there for debugging. For example,

    use typenum::{Integer, N4};

    assert_eq!(N4::to_i32(), -4);

Type operators are traits that behave as functions at the type level. These are the meat of this library. Where possible, traits defined in libcore have been used, but their attached functions have not been implemented.

For example, the `Add` trait is implemented for both unsigned and signed integers, but the `add` function is not. As there are never any objects of the types defined here, it wouldn’t make sense to implement it. What is important is its associated type `Output`, which is where the addition happens.

    use std::ops::Add;
    use typenum::{Integer, P3, P4};

    type X = <P3 as Add<P4>>::Output;
    assert_eq!(<X as Integer>::to_i32(), 7);

In addition, helper aliases are defined for type operators. For example, the above snippet could be replaced with

    use typenum::{Integer, Sum, P3, P4};

    type X = Sum<P3, P4>;
    assert_eq!(<X as Integer>::to_i32(), 7);

Documented in each module is the full list of type operators implemented.

## Re-exports

`pub use crate::array::ATerm;`
`pub use crate::array::TArr;`
`pub use crate::int::NInt;`
`pub use crate::int::PInt;`
`pub use crate::uint::UInt;`
`pub use crate::uint::UTerm;`
`pub use consts::False;`
`pub use consts::True;`
`pub use consts::B0;`
`pub use consts::B1;`
`pub use consts::U0;`
`pub use consts::U1;`
`pub use consts::U2;`
`pub use consts::N1;`
`pub use consts::N2;`
`pub use consts::Z0;`
`pub use consts::P1;`
`pub use consts::P2;`
`pub use crate::marker_traits::*;`
`pub use crate::operator_aliases::*;`
`pub use crate::type_operators::*;`
`pub use consts::*;`
`pub use consts::*;`

## Modules

array
A type-level array of type-level numbers.
bit
Type-level bits.
consts
Type aliases for many constants.
int
Type-level signed integers.
marker_traits
All of the marker traits used in typenum.
operator_aliases
Aliases for the type operators used in this crate. Their purpose is to increase the ergonomics of performing operations on the types defined here. For even more ergonomics, consider using the `op!` macro instead.
type_operators
Useful type operators that are not defined in `core::ops`.
uint
Type-level unsigned integers.

## Macros

assert_type
Asserts that a type is `True`, aka `B1`.
assert_type_eq
Asserts that two types are the same.
cmp Deprecated
A convenience macro for comparing type numbers. Use `op!` instead.
op
Convenient type operations.
tarr
Create a new type-level arrray. Only usable on Rust 1.13.0 or newer.

## Structs

Equal
A potential output from `Cmp`, this is the type equivalent to the enum variant `core::cmp::Ordering::Equal`.
Greater
A potential output from `Cmp`, this is the type equivalent to the enum variant `core::cmp::Ordering::Greater`.
Less
A potential output from `Cmp`, this is the type equivalent to the enum variant `core::cmp::Ordering::Less`.