Macro simple_units::convert_unit

macro_rules! convert_unit {
    ($i1:ident, $i2:ident, $e1:expr, $e2:expr) => { ... };
    ($i1:ident, $i2:ident, $i3:ident) => { ... };
}

This macro implements From for the given units. It either uses a factor or a closure to calculate the conversion

Example:

const factor: f64 = 60.0;
init_unit!(Second);
init_unit!(Minute);
convert_unit!(Second, Minute, factor);