# [−][src]Trait num_traits::identities::One

    pub trait One: Sized + Mul<Self, Output = Self> {
        fn one() -> Self;

        fn set_one(&mut self) { ... }
        fn is_one(&self) -> bool
        where
            Self: PartialEq,
        { ... }
    }

Defines a multiplicative identity element for `Self`.

# Laws

    a * 1 = a       ∀ a ∈ Self
    1 * a = a       ∀ a ∈ Self

## Required methods

### `fn one() -> Self`

Returns the multiplicative identity element of `Self`, `1`.

# Purity

This function should return the same result at all times regardless of external mutable state, for example values stored in TLS or in `static mut`s.

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## Provided methods

### `fn set_one(&mut self)`

Sets `self` to the multiplicative identity element of `Self`, `1`.

### `fn is_one(&self) -> bool where
Self: PartialEq,`

Returns `true` if `self` is equal to the multiplicative identity.

For performance reasons, it's best to implement this manually. After a semver bump, this method will be required, and the `where Self: PartialEq` bound will be removed.

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## Implementations on Foreign Types

### `impl One for usize`[src]

#### `fn one() -> usize`[src]

#### `fn is_one(&self) -> bool`[src]

### `impl One for u8`[src]

#### `fn one() -> u8`[src]

#### `fn is_one(&self) -> bool`[src]

### `impl One for u16`[src]

#### `fn one() -> u16`[src]

#### `fn is_one(&self) -> bool`[src]

### `impl One for u32`[src]

#### `fn one() -> u32`[src]

#### `fn is_one(&self) -> bool`[src]

### `impl One for u64`[src]

#### `fn one() -> u64`[src]

#### `fn is_one(&self) -> bool`[src]

### `impl One for u128`[src]

#### `fn one() -> u128`[src]

#### `fn is_one(&self) -> bool`[src]

### `impl One for isize`[src]

#### `fn one() -> isize`[src]

#### `fn is_one(&self) -> bool`[src]

### `impl One for i8`[src]

#### `fn one() -> i8`[src]

#### `fn is_one(&self) -> bool`[src]

### `impl One for i16`[src]

#### `fn one() -> i16`[src]

#### `fn is_one(&self) -> bool`[src]

### `impl One for i32`[src]

#### `fn one() -> i32`[src]

#### `fn is_one(&self) -> bool`[src]

### `impl One for i64`[src]

#### `fn one() -> i64`[src]

#### `fn is_one(&self) -> bool`[src]

### `impl One for i128`[src]

#### `fn one() -> i128`[src]

#### `fn is_one(&self) -> bool`[src]

### `impl One for f32`[src]

#### `fn one() -> f32`[src]

#### `fn is_one(&self) -> bool`[src]

### `impl One for f64`[src]

#### `fn one() -> f64`[src]

#### `fn is_one(&self) -> bool`[src]

### `impl<T: One> One for Wrapping<T> where
Wrapping<T>: Mul<Output = Wrapping<T>>,` [src]

#### `fn set_one(&mut self)`[src]

#### `fn one() -> Self`[src]

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## Implementors

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