2 stable releases
1.1.0 | Aug 7, 2023 |
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1.0.0 | Aug 6, 2023 |
#2875 in Rust patterns
Used in 2 crates
(via cartesian_array_product)
4KB
const-anonymous-functions
Small crate that provides a macro to create anonymous functions that can be used in const contexts.
It doesn't provide any new functionality, only syntax sugar.
Usage
Add it to your project
cargo add const-anonymous-functions
Example
use const_anonymous_functions::caf;
const RESULT: i32 = caf!(|a: i32, b: i32| -> i32 { a + b })(1, 2);
assert_eq!(RESULT, 1 + 2);
Caveats
There are a couple caveats to using this crate:
- You must always annotate the type of the function (both arguments and return type)
- To avoid confusion, you must always use braces in the function body, so something like
|a: i32| a + 1
is not allowed (notice how it would be wrong either way since the return type here is()
, so it doesn't return anything).|a: i32| -> i32 { a + 1 }
is the correct way to write it.
How it works
This macro is actually super basic. It just takes the closure syntax and transforms it into a const function. Then it returns the function.
So caf!(|a: i32, b: i32| -> i32 { a + b })
literally becomes:
{
const fn __annon_caf__(a: i32, b: i32) -> i32 {
a + b
}
__annon_caf__
}
# ;
That's it.