Crate num_lazy

num-lazy helps you write numbers for generic-typed functions.

use num_lazy::declare_nums;
use num_traits::Float;
// Assign to generic type T.
// Important. Use the braces!
declare_nums!{T}

fn circumference<T: Float>(radius: T) -> T {
    two!() * pi!() * radius
}

See what numbers are declared in declare_nums.

If you declare_nums!() in the root of your crate, you don’t even need to import the macros to submodules. This will not re-export the macros to the public crate.

lib.rs or main.rs

use num_lazy::declare_nums;
declare_nums!{T}

// My submodules
pub mod generic_math;

generic_math.rs

pub fn circle_area<T: Float>(radius: T) -> T {
    pi!() * radius * radius
}

If you want to declare the numbers in the root of your crate but keep the macro contained in a module, you can simply:

lib.rs or main.rs

mod generics {
    use num_lazy::declare_nums;
    declare_nums!{T}
}

generic_math.rs

use crate::generics::*;

pub fn circle_area<T: Float>(radius: T) -> T {
    pi!() * radius * radius
}

Macros

declare_nums

Declare commonly used num generics in the module or crate root.