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## NonZeroI64

# Type Alias NonZeroI64

1.34.0 · Source

    pub type NonZeroI64 = NonZero<i64>;

Expand description

An `i64` that is known not to equal zero.

This enables some memory layout optimization. For example, `Option<NonZeroI64>` is the same size as `i64`:

    assert_eq!(size_of::<Option<core::num::NonZeroI64>>(), size_of::<i64>());

## §Layout

`NonZeroI64` is guaranteed to have the same layout and bit validity as `i64` with the exception that `0` is not a valid instance. `Option<NonZeroI64>` is guaranteed to be compatible with `i64`, including in FFI.

Thanks to the null pointer optimization, `NonZeroI64` and `Option<NonZeroI64>` are guaranteed to have the same size and alignment:

    use std::num::NonZeroI64;

    assert_eq!(size_of::<NonZeroI64>(), size_of::<Option<NonZeroI64>>());
    assert_eq!(align_of::<NonZeroI64>(), align_of::<Option<NonZeroI64>>());

## §Compile-time creation

Since both `Option::unwrap()` and `Option::expect()` are `const`, it is possible to define a new `NonZeroI64` at compile time via:

    use std::num::NonZeroI64;

    const TEN: NonZeroI64 = NonZeroI64::new(10).expect("ten is non-zero");

## Aliased Type§

    pub struct NonZeroI64(/* private fields */);