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# const_fn_assert
[](https://travis-ci.com/powlpy/const_fn_assert)
[](https://crates.io/crates/const_fn_assert)
[](https://docs.rs/const_fn_assert)
[](https://github.com/powlpy/const_fn_assert/blob/master/LICENSE)
This crate provide macros assertions who can be used in `const` function.
- [Documentation](https://docs.rs/const_fn_assert)
- [Release notes](https://github.com/powlpy/const_fn_assert/releases)
## Example
```rust
const fn my_const_fn(x: u8) -> u8 {
cfn_assert!(x < 5);
x + 1
}
const _CONST: u8 = my_const_fn(1);
fn main() {
let _var = my_const_fn(2);
}
```
The function below panic when running :
```rust
fn fail() {
let _var = my_const_fn(6); //thread 'main' panicked at 'index out of bounds: the len is 1 but the index is 1'
}
```
And this code don't compile :
```rust
const _CONST: u8 = my_const_fn(6); //~ ERROR any use of this value will cause an error
```
Available macros are `cfn_assert`, `cfn_assert_eq`, `cfn_assert_ne`, `cfn_debug_assert`, `cfn_debug_assert_eq` and `cfn_debug_assert_ne`.
## Installation
This crate is available
[on crates.io](https://crates.io/crates/const_fn_assert) and can be used by
adding the following to your project's
[`Cargo.toml`](https://doc.rust-lang.org/cargo/reference/manifest.html):
```toml
[dependencies]
const_fn_assert = "0.1"
```
and this to your crate root (`main.rs` or `lib.rs`):
```rust
#[macro_use]
extern crate const_fn_assert;
```
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