# cutlass
> experimental auto-currying for rust functions
### example
this currently works only on nightly with the
`type_alias_impl_trait` feature enabled.
```rust
#![feature(type_alias_impl_trait)]
#[cutlass::curry]
fn add(x: u32, y: u32, z: u32) -> u32 {
return x + y + z;
}
fn main() {
let plus_3 = add(1)(2);
let v: Vec<u32> = (1..=3).map(plus_3).collect();
assert_eq!(v, vec![4, 5, 6]);
}
```
### how it works
the `#[curry]` proc-macro expands the above `add` function to
something like this (roughly):
```rust
type T0 = u32;
type T1 = impl Fn(u32) -> T0;
type T2 = impl Fn(u32) -> T1;
fn add(x: u32) -> T2 {
return (move |y| move |z| x + y + z);
}
```
### gotchas
- doesn't yet work for method functions (signatures with
`self`)
- the function has to have a return value
- works only on nightly with `type_alias_impl_trait`
enabled
### testing
test this crate with `cargo +nightly test`.
to view macro expansions, install `cargo-expand` and run `cargo expand
--test <test name>`. expand `tests/smoke.rs` for example:
```
cargo expand --test smoke
```