# [−][src]Trait num::traits::cast::FromPrimitive

    pub trait FromPrimitive {
        fn from_i64(n: i64) -> Option<Self>;
        fn from_u64(n: u64) -> Option<Self>;

        fn from_isize(n: isize) -> Option<Self> { ... }
        fn from_i8(n: i8) -> Option<Self> { ... }
        fn from_i16(n: i16) -> Option<Self> { ... }
        fn from_i32(n: i32) -> Option<Self> { ... }
        fn from_i128(n: i128) -> Option<Self> { ... }
        fn from_usize(n: usize) -> Option<Self> { ... }
        fn from_u8(n: u8) -> Option<Self> { ... }
        fn from_u16(n: u16) -> Option<Self> { ... }
        fn from_u32(n: u32) -> Option<Self> { ... }
        fn from_u128(n: u128) -> Option<Self> { ... }
        fn from_f32(n: f32) -> Option<Self> { ... }
        fn from_f64(n: f64) -> Option<Self> { ... }
    }

A generic trait for converting a number to a value.

## Required methods

### `fn from_i64(n: i64) -> Option<Self>`

Convert an `i64` to return an optional value of this type. If the type cannot be represented by this value, then `None` is returned.

### `fn from_u64(n: u64) -> Option<Self>`

Convert an `u64` to return an optional value of this type. If the type cannot be represented by this value, then `None` is returned.

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## Provided methods

### `fn from_isize(n: isize) -> Option<Self>`

Convert an `isize` to return an optional value of this type. If the value cannot be represented by this value, then `None` is returned.

### `fn from_i8(n: i8) -> Option<Self>`

Convert an `i8` to return an optional value of this type. If the type cannot be represented by this value, then `None` is returned.

### `fn from_i16(n: i16) -> Option<Self>`

Convert an `i16` to return an optional value of this type. If the type cannot be represented by this value, then `None` is returned.

### `fn from_i32(n: i32) -> Option<Self>`

Convert an `i32` to return an optional value of this type. If the type cannot be represented by this value, then `None` is returned.

### `fn from_i128(n: i128) -> Option<Self>`

Convert an `i128` to return an optional value of this type. If the type cannot be represented by this value, then `None` is returned.

This method is only available with feature `i128` enabled on Rust >= 1.26.

The default implementation converts through `from_i64()`. Types implementing this trait should override this method if they can represent a greater range.

### `fn from_usize(n: usize) -> Option<Self>`

Convert a `usize` to return an optional value of this type. If the type cannot be represented by this value, then `None` is returned.

### `fn from_u8(n: u8) -> Option<Self>`

Convert an `u8` to return an optional value of this type. If the type cannot be represented by this value, then `None` is returned.

### `fn from_u16(n: u16) -> Option<Self>`

Convert an `u16` to return an optional value of this type. If the type cannot be represented by this value, then `None` is returned.

### `fn from_u32(n: u32) -> Option<Self>`

Convert an `u32` to return an optional value of this type. If the type cannot be represented by this value, then `None` is returned.

### `fn from_u128(n: u128) -> Option<Self>`

Convert an `u128` to return an optional value of this type. If the type cannot be represented by this value, then `None` is returned.

This method is only available with feature `i128` enabled on Rust >= 1.26.

The default implementation converts through `from_u64()`. Types implementing this trait should override this method if they can represent a greater range.

### `fn from_f32(n: f32) -> Option<Self>`

Convert a `f32` to return an optional value of this type. If the type cannot be represented by this value, then `None` is returned.

### `fn from_f64(n: f64) -> Option<Self>`

Convert a `f64` to return an optional value of this type. If the type cannot be represented by this value, then `None` is returned.

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## Implementations on Foreign Types

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

#### `fn from_isize(n: isize) -> Option<u32>`[src]

#### `fn from_i8(n: i8) -> Option<u32>`[src]

#### `fn from_i16(n: i16) -> Option<u32>`[src]

#### `fn from_i32(n: i32) -> Option<u32>`[src]

#### `fn from_i64(n: i64) -> Option<u32>`[src]

#### `fn from_i128(n: i128) -> Option<u32>`[src]

#### `fn from_usize(n: usize) -> Option<u32>`[src]

#### `fn from_u8(n: u8) -> Option<u32>`[src]

#### `fn from_u16(n: u16) -> Option<u32>`[src]

#### `fn from_u32(n: u32) -> Option<u32>`[src]

#### `fn from_u64(n: u64) -> Option<u32>`[src]

#### `fn from_u128(n: u128) -> Option<u32>`[src]

#### `fn from_f32(n: f32) -> Option<u32>`[src]

#### `fn from_f64(n: f64) -> Option<u32>`[src]

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

#### `fn from_isize(n: isize) -> Option<i64>`[src]

#### `fn from_i8(n: i8) -> Option<i64>`[src]

#### `fn from_i16(n: i16) -> Option<i64>`[src]

#### `fn from_i32(n: i32) -> Option<i64>`[src]

#### `fn from_i64(n: i64) -> Option<i64>`[src]

#### `fn from_i128(n: i128) -> Option<i64>`[src]

#### `fn from_usize(n: usize) -> Option<i64>`[src]

#### `fn from_u8(n: u8) -> Option<i64>`[src]

#### `fn from_u16(n: u16) -> Option<i64>`[src]

#### `fn from_u32(n: u32) -> Option<i64>`[src]

#### `fn from_u64(n: u64) -> Option<i64>`[src]

#### `fn from_u128(n: u128) -> Option<i64>`[src]

#### `fn from_f32(n: f32) -> Option<i64>`[src]

#### `fn from_f64(n: f64) -> Option<i64>`[src]

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

#### `fn from_isize(n: isize) -> Option<f32>`[src]

#### `fn from_i8(n: i8) -> Option<f32>`[src]

#### `fn from_i16(n: i16) -> Option<f32>`[src]

#### `fn from_i32(n: i32) -> Option<f32>`[src]

#### `fn from_i64(n: i64) -> Option<f32>`[src]

#### `fn from_i128(n: i128) -> Option<f32>`[src]

#### `fn from_usize(n: usize) -> Option<f32>`[src]

#### `fn from_u8(n: u8) -> Option<f32>`[src]

#### `fn from_u16(n: u16) -> Option<f32>`[src]

#### `fn from_u32(n: u32) -> Option<f32>`[src]

#### `fn from_u64(n: u64) -> Option<f32>`[src]

#### `fn from_u128(n: u128) -> Option<f32>`[src]

#### `fn from_f32(n: f32) -> Option<f32>`[src]

#### `fn from_f64(n: f64) -> Option<f32>`[src]

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

#### `fn from_isize(n: isize) -> Option<i32>`[src]

#### `fn from_i8(n: i8) -> Option<i32>`[src]

#### `fn from_i16(n: i16) -> Option<i32>`[src]

#### `fn from_i32(n: i32) -> Option<i32>`[src]

#### `fn from_i64(n: i64) -> Option<i32>`[src]

#### `fn from_i128(n: i128) -> Option<i32>`[src]

#### `fn from_usize(n: usize) -> Option<i32>`[src]

#### `fn from_u8(n: u8) -> Option<i32>`[src]

#### `fn from_u16(n: u16) -> Option<i32>`[src]

#### `fn from_u32(n: u32) -> Option<i32>`[src]

#### `fn from_u64(n: u64) -> Option<i32>`[src]

#### `fn from_u128(n: u128) -> Option<i32>`[src]

#### `fn from_f32(n: f32) -> Option<i32>`[src]

#### `fn from_f64(n: f64) -> Option<i32>`[src]

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

#### `fn from_isize(n: isize) -> Option<u128>`[src]

#### `fn from_i8(n: i8) -> Option<u128>`[src]

#### `fn from_i16(n: i16) -> Option<u128>`[src]

#### `fn from_i32(n: i32) -> Option<u128>`[src]

#### `fn from_i64(n: i64) -> Option<u128>`[src]

#### `fn from_i128(n: i128) -> Option<u128>`[src]

#### `fn from_usize(n: usize) -> Option<u128>`[src]

#### `fn from_u8(n: u8) -> Option<u128>`[src]

#### `fn from_u16(n: u16) -> Option<u128>`[src]

#### `fn from_u32(n: u32) -> Option<u128>`[src]

#### `fn from_u64(n: u64) -> Option<u128>`[src]

#### `fn from_u128(n: u128) -> Option<u128>`[src]

#### `fn from_f32(n: f32) -> Option<u128>`[src]

#### `fn from_f64(n: f64) -> Option<u128>`[src]

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

#### `fn from_isize(n: isize) -> Option<i128>`[src]

#### `fn from_i8(n: i8) -> Option<i128>`[src]

#### `fn from_i16(n: i16) -> Option<i128>`[src]

#### `fn from_i32(n: i32) -> Option<i128>`[src]

#### `fn from_i64(n: i64) -> Option<i128>`[src]

#### `fn from_i128(n: i128) -> Option<i128>`[src]

#### `fn from_usize(n: usize) -> Option<i128>`[src]

#### `fn from_u8(n: u8) -> Option<i128>`[src]

#### `fn from_u16(n: u16) -> Option<i128>`[src]

#### `fn from_u32(n: u32) -> Option<i128>`[src]

#### `fn from_u64(n: u64) -> Option<i128>`[src]

#### `fn from_u128(n: u128) -> Option<i128>`[src]

#### `fn from_f32(n: f32) -> Option<i128>`[src]

#### `fn from_f64(n: f64) -> Option<i128>`[src]

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

#### `fn from_isize(n: isize) -> Option<usize>`[src]

#### `fn from_i8(n: i8) -> Option<usize>`[src]

#### `fn from_i16(n: i16) -> Option<usize>`[src]

#### `fn from_i32(n: i32) -> Option<usize>`[src]

#### `fn from_i64(n: i64) -> Option<usize>`[src]

#### `fn from_i128(n: i128) -> Option<usize>`[src]

#### `fn from_usize(n: usize) -> Option<usize>`[src]

#### `fn from_u8(n: u8) -> Option<usize>`[src]

#### `fn from_u16(n: u16) -> Option<usize>`[src]

#### `fn from_u32(n: u32) -> Option<usize>`[src]

#### `fn from_u64(n: u64) -> Option<usize>`[src]

#### `fn from_u128(n: u128) -> Option<usize>`[src]

#### `fn from_f32(n: f32) -> Option<usize>`[src]

#### `fn from_f64(n: f64) -> Option<usize>`[src]

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

#### `fn from_isize(n: isize) -> Option<u16>`[src]

#### `fn from_i8(n: i8) -> Option<u16>`[src]

#### `fn from_i16(n: i16) -> Option<u16>`[src]

#### `fn from_i32(n: i32) -> Option<u16>`[src]

#### `fn from_i64(n: i64) -> Option<u16>`[src]

#### `fn from_i128(n: i128) -> Option<u16>`[src]

#### `fn from_usize(n: usize) -> Option<u16>`[src]

#### `fn from_u8(n: u8) -> Option<u16>`[src]

#### `fn from_u16(n: u16) -> Option<u16>`[src]

#### `fn from_u32(n: u32) -> Option<u16>`[src]

#### `fn from_u64(n: u64) -> Option<u16>`[src]

#### `fn from_u128(n: u128) -> Option<u16>`[src]

#### `fn from_f32(n: f32) -> Option<u16>`[src]

#### `fn from_f64(n: f64) -> Option<u16>`[src]

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

#### `fn from_isize(n: isize) -> Option<u8>`[src]

#### `fn from_i8(n: i8) -> Option<u8>`[src]

#### `fn from_i16(n: i16) -> Option<u8>`[src]

#### `fn from_i32(n: i32) -> Option<u8>`[src]

#### `fn from_i64(n: i64) -> Option<u8>`[src]

#### `fn from_i128(n: i128) -> Option<u8>`[src]

#### `fn from_usize(n: usize) -> Option<u8>`[src]

#### `fn from_u8(n: u8) -> Option<u8>`[src]

#### `fn from_u16(n: u16) -> Option<u8>`[src]

#### `fn from_u32(n: u32) -> Option<u8>`[src]

#### `fn from_u64(n: u64) -> Option<u8>`[src]

#### `fn from_u128(n: u128) -> Option<u8>`[src]

#### `fn from_f32(n: f32) -> Option<u8>`[src]

#### `fn from_f64(n: f64) -> Option<u8>`[src]

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

#### `fn from_isize(n: isize) -> Option<i8>`[src]

#### `fn from_i8(n: i8) -> Option<i8>`[src]

#### `fn from_i16(n: i16) -> Option<i8>`[src]

#### `fn from_i32(n: i32) -> Option<i8>`[src]

#### `fn from_i64(n: i64) -> Option<i8>`[src]

#### `fn from_i128(n: i128) -> Option<i8>`[src]

#### `fn from_usize(n: usize) -> Option<i8>`[src]

#### `fn from_u8(n: u8) -> Option<i8>`[src]

#### `fn from_u16(n: u16) -> Option<i8>`[src]

#### `fn from_u32(n: u32) -> Option<i8>`[src]

#### `fn from_u64(n: u64) -> Option<i8>`[src]

#### `fn from_u128(n: u128) -> Option<i8>`[src]

#### `fn from_f32(n: f32) -> Option<i8>`[src]

#### `fn from_f64(n: f64) -> Option<i8>`[src]

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

#### `fn from_isize(n: isize) -> Option<u64>`[src]

#### `fn from_i8(n: i8) -> Option<u64>`[src]

#### `fn from_i16(n: i16) -> Option<u64>`[src]

#### `fn from_i32(n: i32) -> Option<u64>`[src]

#### `fn from_i64(n: i64) -> Option<u64>`[src]

#### `fn from_i128(n: i128) -> Option<u64>`[src]

#### `fn from_usize(n: usize) -> Option<u64>`[src]

#### `fn from_u8(n: u8) -> Option<u64>`[src]

#### `fn from_u16(n: u16) -> Option<u64>`[src]

#### `fn from_u32(n: u32) -> Option<u64>`[src]

#### `fn from_u64(n: u64) -> Option<u64>`[src]

#### `fn from_u128(n: u128) -> Option<u64>`[src]

#### `fn from_f32(n: f32) -> Option<u64>`[src]

#### `fn from_f64(n: f64) -> Option<u64>`[src]

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

#### `fn from_isize(n: isize) -> Option<i16>`[src]

#### `fn from_i8(n: i8) -> Option<i16>`[src]

#### `fn from_i16(n: i16) -> Option<i16>`[src]

#### `fn from_i32(n: i32) -> Option<i16>`[src]

#### `fn from_i64(n: i64) -> Option<i16>`[src]

#### `fn from_i128(n: i128) -> Option<i16>`[src]

#### `fn from_usize(n: usize) -> Option<i16>`[src]

#### `fn from_u8(n: u8) -> Option<i16>`[src]

#### `fn from_u16(n: u16) -> Option<i16>`[src]

#### `fn from_u32(n: u32) -> Option<i16>`[src]

#### `fn from_u64(n: u64) -> Option<i16>`[src]

#### `fn from_u128(n: u128) -> Option<i16>`[src]

#### `fn from_f32(n: f32) -> Option<i16>`[src]

#### `fn from_f64(n: f64) -> Option<i16>`[src]

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

#### `fn from_isize(n: isize) -> Option<f64>`[src]

#### `fn from_i8(n: i8) -> Option<f64>`[src]

#### `fn from_i16(n: i16) -> Option<f64>`[src]

#### `fn from_i32(n: i32) -> Option<f64>`[src]

#### `fn from_i64(n: i64) -> Option<f64>`[src]

#### `fn from_i128(n: i128) -> Option<f64>`[src]

#### `fn from_usize(n: usize) -> Option<f64>`[src]

#### `fn from_u8(n: u8) -> Option<f64>`[src]

#### `fn from_u16(n: u16) -> Option<f64>`[src]

#### `fn from_u32(n: u32) -> Option<f64>`[src]

#### `fn from_u64(n: u64) -> Option<f64>`[src]

#### `fn from_u128(n: u128) -> Option<f64>`[src]

#### `fn from_f32(n: f32) -> Option<f64>`[src]

#### `fn from_f64(n: f64) -> Option<f64>`[src]

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

#### `fn from_isize(n: isize) -> Option<isize>`[src]

#### `fn from_i8(n: i8) -> Option<isize>`[src]

#### `fn from_i16(n: i16) -> Option<isize>`[src]

#### `fn from_i32(n: i32) -> Option<isize>`[src]

#### `fn from_i64(n: i64) -> Option<isize>`[src]

#### `fn from_i128(n: i128) -> Option<isize>`[src]

#### `fn from_usize(n: usize) -> Option<isize>`[src]

#### `fn from_u8(n: u8) -> Option<isize>`[src]

#### `fn from_u16(n: u16) -> Option<isize>`[src]

#### `fn from_u32(n: u32) -> Option<isize>`[src]

#### `fn from_u64(n: u64) -> Option<isize>`[src]

#### `fn from_u128(n: u128) -> Option<isize>`[src]

#### `fn from_f32(n: f32) -> Option<isize>`[src]

#### `fn from_f64(n: f64) -> Option<isize>`[src]

### `impl<T> FromPrimitive for Wrapping<T> where
T: FromPrimitive,` [src]

#### `fn from_isize(n: isize) -> Option<Wrapping<T>>`[src]

#### `fn from_i8(n: i8) -> Option<Wrapping<T>>`[src]

#### `fn from_i16(n: i16) -> Option<Wrapping<T>>`[src]

#### `fn from_i32(n: i32) -> Option<Wrapping<T>>`[src]

#### `fn from_i64(n: i64) -> Option<Wrapping<T>>`[src]

#### `fn from_i128(n: i128) -> Option<Wrapping<T>>`[src]

#### `fn from_usize(n: usize) -> Option<Wrapping<T>>`[src]

#### `fn from_u8(n: u8) -> Option<Wrapping<T>>`[src]

#### `fn from_u16(n: u16) -> Option<Wrapping<T>>`[src]

#### `fn from_u32(n: u32) -> Option<Wrapping<T>>`[src]

#### `fn from_u64(n: u64) -> Option<Wrapping<T>>`[src]

#### `fn from_u128(n: u128) -> Option<Wrapping<T>>`[src]

#### `fn from_f32(n: f32) -> Option<Wrapping<T>>`[src]

#### `fn from_f64(n: f64) -> Option<Wrapping<T>>`[src]

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## Implementors

### `impl FromPrimitive for BigInt`[src]

#### `fn from_i64(n: i64) -> Option<BigInt>`[src]

#### `fn from_u64(n: u64) -> Option<BigInt>`[src]

#### `fn from_f64(n: f64) -> Option<BigInt>`[src]

### `impl FromPrimitive for BigUint`[src]

#### `fn from_i64(n: i64) -> Option<BigUint>`[src]

#### `fn from_u64(n: u64) -> Option<BigUint>`[src]

#### `fn from_f64(n: f64) -> Option<BigUint>`[src]

### `impl FromPrimitive for Ratio<i16>`[src]

#### `fn from_i64(n: i64) -> Option<Ratio<i16>>`[src]

#### `fn from_u64(n: u64) -> Option<Ratio<i16>>`[src]

#### `fn from_f32(n: f32) -> Option<Ratio<i16>>`[src]

#### `fn from_f64(n: f64) -> Option<Ratio<i16>>`[src]

### `impl FromPrimitive for Ratio<i32>`[src]

#### `fn from_i64(n: i64) -> Option<Ratio<i32>>`[src]

#### `fn from_u64(n: u64) -> Option<Ratio<i32>>`[src]

#### `fn from_f32(n: f32) -> Option<Ratio<i32>>`[src]

#### `fn from_f64(n: f64) -> Option<Ratio<i32>>`[src]

### `impl FromPrimitive for Ratio<i64>`[src]

#### `fn from_i64(n: i64) -> Option<Ratio<i64>>`[src]

#### `fn from_u64(n: u64) -> Option<Ratio<i64>>`[src]

#### `fn from_f32(n: f32) -> Option<Ratio<i64>>`[src]

#### `fn from_f64(n: f64) -> Option<Ratio<i64>>`[src]

### `impl FromPrimitive for Ratio<i8>`[src]

#### `fn from_i64(n: i64) -> Option<Ratio<i8>>`[src]

#### `fn from_u64(n: u64) -> Option<Ratio<i8>>`[src]

#### `fn from_f32(n: f32) -> Option<Ratio<i8>>`[src]

#### `fn from_f64(n: f64) -> Option<Ratio<i8>>`[src]

### `impl FromPrimitive for Ratio<isize>`[src]

#### `fn from_i64(n: i64) -> Option<Ratio<isize>>`[src]

#### `fn from_u64(n: u64) -> Option<Ratio<isize>>`[src]

#### `fn from_f32(n: f32) -> Option<Ratio<isize>>`[src]

#### `fn from_f64(n: f64) -> Option<Ratio<isize>>`[src]

### `impl FromPrimitive for Ratio<u16>`[src]

#### `fn from_i64(n: i64) -> Option<Ratio<u16>>`[src]

#### `fn from_u64(n: u64) -> Option<Ratio<u16>>`[src]

#### `fn from_f32(n: f32) -> Option<Ratio<u16>>`[src]

#### `fn from_f64(n: f64) -> Option<Ratio<u16>>`[src]

### `impl FromPrimitive for Ratio<u32>`[src]

#### `fn from_i64(n: i64) -> Option<Ratio<u32>>`[src]

#### `fn from_u64(n: u64) -> Option<Ratio<u32>>`[src]

#### `fn from_f32(n: f32) -> Option<Ratio<u32>>`[src]

#### `fn from_f64(n: f64) -> Option<Ratio<u32>>`[src]

### `impl FromPrimitive for Ratio<u64>`[src]

#### `fn from_i64(n: i64) -> Option<Ratio<u64>>`[src]

#### `fn from_u64(n: u64) -> Option<Ratio<u64>>`[src]

#### `fn from_f32(n: f32) -> Option<Ratio<u64>>`[src]

#### `fn from_f64(n: f64) -> Option<Ratio<u64>>`[src]

### `impl FromPrimitive for Ratio<u8>`[src]

#### `fn from_i64(n: i64) -> Option<Ratio<u8>>`[src]

#### `fn from_u64(n: u64) -> Option<Ratio<u8>>`[src]

#### `fn from_f32(n: f32) -> Option<Ratio<u8>>`[src]

#### `fn from_f64(n: f64) -> Option<Ratio<u8>>`[src]

### `impl FromPrimitive for Ratio<usize>`[src]

#### `fn from_i64(n: i64) -> Option<Ratio<usize>>`[src]

#### `fn from_u64(n: u64) -> Option<Ratio<usize>>`[src]

#### `fn from_f32(n: f32) -> Option<Ratio<usize>>`[src]

#### `fn from_f64(n: f64) -> Option<Ratio<usize>>`[src]

### `impl FromPrimitive for Ratio<BigInt>`[src]

#### `fn from_i64(n: i64) -> Option<Ratio<BigInt>>`[src]

#### `fn from_u64(n: u64) -> Option<Ratio<BigInt>>`[src]

#### `fn from_f32(n: f32) -> Option<Ratio<BigInt>>`[src]

#### `fn from_f64(n: f64) -> Option<Ratio<BigInt>>`[src]

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## Search Tricks

Prefix searches with a type followed by a colon (e.g., `fn:`) to restrict the search to a given type.

Accepted types are: `fn`, `mod`, `struct`, `enum`, `trait`, `type`, `macro`, and `const`.

Search functions by type signature (e.g., `vec -> usize` or `* -> vec`)

Search multiple things at once by splitting your query with comma (e.g., `str,u8` or `String,struct:Vec,test`)