# Crate as_num[−][src]

This module implements a very opinionated approach to converting numbers.

Imagine you have a function `return_u32`

returning an `u32`

, and you would like to pass its return value into some
other function `take_i8`

, taking an `i8`

:

Then, the compiler (correctly) complains as soon as you write `take_i8(return_u32())`

.
I came into those situations frequently, so I simply changed it to
`take_i8(return_u32() as i8)`

. However, when doing so, I implicitly assumed that the semantic
meaning of the number does not change, i.e. I assume that `i8`

is capable of representing the
exact same value that `return_u32`

gives me (which is not the case in the example shown).

This module enables you to write the following:

use as_num::AsNum; // AsNum is the trait enabling the conversions fn return_u32() -> u32 { 42 } fn take_i8(_i: i8) { } take_i8(return_u32().as_num())

`as_num`

converts its argument into the destination type, thereby checking whether the
conversion can be done without loss of data.

It tries to follow a similar approach to the one that is chosen with e.g. "normal addition" and `checked_add`

:
It offers one method `as_num`

that does the conversion (at last going down to Rust's `as`

), and
`debug_assert`

s that the conversion is lossless.
In addition to `as_num`

, it offers a method `checked_as_num`

, returning an `Option`

.

This module implements conversion for any combination of the following types:
`i8`

, `i16`

, `i32`

, `i64`

, `isize`

, `u8`

, `u16`

, `u32`

, `u64`

, `usize`

, `f32`

, `f64`

.

The function `as_num`

`debug_assert`

s that the destination value is convertible back to the
exact same source value.

That, in particular, means that converting floating-point to integral numbers can only be done
with `as_num`

if the source is already been rounded to some integral number.

## Traits

AsNum | |

AsNumInternal | |

SignedInt | |

UnsignedInt |