core::mem::discriminant - Rust
Description: API documentation for the Rust `discriminant` fn in crate `core`.
Keywords: rust, rustlang, rust-lang, discriminant

# Function core::mem::discriminant [−] [src]

    pub fn discriminant<T>(v: &T) -> Discriminant<T>

🔬 This is a nightly-only experimental API. (`discriminant_value` #24263)

recently added, follows RFC

Returns a value uniquely identifying the enum variant in `v`.

If `T` is not an enum, calling this function will not result in undefined behavior, but the return value is unspecified.

# Stability

The discriminant of an enum variant may change if the enum definition changes. A discriminant of some variant will not change between compilations with the same compiler.

# Examples

This can be used to compare enums that carry data, while disregarding the actual data:

    #![feature(discriminant_value)]
    use std::mem;

    enum Foo { A(&'static str), B(i32), C(i32) }

    assert!(mem::discriminant(&Foo::A("bar")) == mem::discriminant(&Foo::A("baz")));
    assert!(mem::discriminant(&Foo::B(1))     == mem::discriminant(&Foo::B(2)));
    assert!(mem::discriminant(&Foo::B(3))     != mem::discriminant(&Foo::C(3)));Run

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