# ilog

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## Base 10 and 2 logarithm functions for integer types

The `IntLog` trait defines the following methods:

```rust
fn log10(self) -> usize
fn log2(self) -> usize
fn checked_log10(self) -> Option<usize>
fn checked_log2(self) -> Option<usize>
```

The `log2` and `log10` methods are optimized for the integer width and are
`[inline]` since the code remains small enough. They typically use constant tables
that are only stored once, even if the methods using them are inlined multiple times.

The **checked** versions of the methods, `checked_log2` and `checked_log10`,
return `None` if the logarithm is undefined for the parameter value, whereas the unchecked
methods mentioned above simply panic or return a wrong value.

## Examples

```rust
use ilog::IntLog;

let hundred: u32 = 100;
assert_eq!(hundred.log10(), 2);
assert_eq!(u32::log10(99), 1);

let value: u64 = 256;
assert_eq!(value.log2(), 8);
assert_eq!(u64::log2(255), 7);

assert_eq!(u32::checked_log2(63), Some(5));
assert_eq!(0_u32.checked_log2(), None);
```

## Compatibility

The `ilog` crate is tested for rustc 1.65 and greater, on Windows 64-bit and Linux 64/32-bit platforms.

It doesn't require the `std` library, and supports 16-, 32- and 64-bit architectures.

### Rust versions 1.64 and earlier

Note that in versions 1.64 and earlier, `log`, `log2` and `log10` were nightly experimental `core::num` methods, which were then [renamed](https://github.com/rust-lang/rust/commit/c18f22058bc351224ad2b89e9d352e050275f475)
respectively to `ilog`, `ilog2` and `ilog10` in version 1.65 (and are still experimental). This was unknown to the author when the
crate was first published.

Should you need to use this crate with earlier versions of rustc, the warnings can be masked with this file directive:

```rust
    #![allow(unstable_name_collisions)]
```

or with this directive in front of the function using the methods:

```rust
    #[allow(unstable_name_collisions)]
```

## Releases

[RELEASES.md](RELEASES.md) keeps a log of all the releases.

## License

Licensed under [MIT license](https://choosealicense.com/licenses/mit/).