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#![feature(concat_idents)]
#![deny(missing_docs)]

//! Macro for underscore named argumet syntax, aka [Dyon](https://github.com/pistondevelopers/dyon).
//!
//! This library requires Rust 2018 nightly and only works for functions, not methods.
//!
//! By naming a function `line__color_from_to`, one can call it like this:
//!
//! ```ignore
//! args!(line(color: [1.0; 4], from: [0.0, 0.0], to: [100.0, 100.0]))
//! ```
//!
//! - Double underscore after function name and before the name of the first argument
//! - Single underscore separating arguments
//!
//! ### Example
//!
//! ```rust
//! #![feature(concat_idents)]
//!
//! use underscore_args::args;
//!
//! #[allow(non_snake_case)]
//! fn line__color_from_to(_color: [f32; 4], _from: [f32; 2], _to: [f32; 2]) {}
//!
//! args!(line(color: [1.0; 4], from: [0.0, 0.0], to: [100.0, 100.0]));
//! ```

#[macro_export]
macro_rules! args {($x:ident ( $($y:ident : $z:expr),* $(,)* )) =>
    {concat_idents!($x, _, $(_,$y),*)($($z),*)}}

#[cfg(test)]
mod tests {
    #[test]
    fn it_works() {
        #[allow(non_snake_case)]
        fn clear__color(_color: [f32; 4]) {}
        #[allow(non_snake_case)]
        fn line__color_from_to(_color: [f32; 4], _from: [f32; 2], _to: [f32; 2]) {}
        #[allow(non_snake_case)]
        fn person__fname_lname_age_city_country_planet(
            _first_name: &str,
            _last_name: &str,
            _age: u8,
            _city: &str,
            _country: &str,
            _planet: &str,
        ) {}

        args!(clear(color: [1.0; 4]));
        args!(clear(color: [1.0; 4],));
        args!(line(color: [1.0; 4], from: [0.0, 0.0], to: [100.0, 100.0]));
        args!(person(
            fname: "Homer",
            lname: "Simpson",
            age: 42,
            city: "Springfield",
            country: "US",
            planet: "Earth"
        ));
    }
}