Macro metron::def_quantity

macro_rules! def_quantity {
    (
        $(#[$meta_for_quantity:meta])*
        $vis:vis $quantity:ident
        $(#[$meta_for_base_unit:meta])*
        < $unit:ty >;
    ) => { ... };
    (
        $(#[$meta_for_quantity:meta])*
        $vis:vis $quantity:ident
        $(#[$meta_for_base_unit:meta])*
        < $unit:ty > {
        $(
            $(#[$meta_for_from:meta])*
            from $from_body:tt ,
        )*
        // $(into $into_body:tt ,)*
        $(sym   $sym_body:tt ,)?
        // $(dim   $dim_body:tt ,)?
    }) => { ... };
}

Generate define of Quantity

Examples

Define Length

use metron_core::{def_unit, def_quantity};
def_unit!{pub Metre{ from (Feet =*0.3048), }}
def_unit!{pub Feet;}

def_quantity!{
    /// Length is a measure of distance.
    pub Length<Metre> {
        from( Feet ),
    }
}

if you write abobe macro will generates like below

use metron_core::{def_unit, Quantity, FromUnit};
def_unit!{pub Metre{ from (Feet =* 0.3048), }}
def_unit!{pub Feet;}

/// Length is a measure of distance.
pub struct Length;

impl metron_core::Quantity for Length {
    type BaseUnit = Metre;
}

impl <N> FromUnit<N, Metre> for Length{
    type Output = <Metre as FromUnit<N, Metre>>::Output;
    fn from_unit(num: N) -> Self::Output {
        /* conversion */
        num
    }
}

impl <N> FromUnit<N, Feet> for Length {
    type Output = <<Self as Quantity>::BaseUnit as FromUnit<N, Metre>>::Output;
    fn from_unit(num: N) -> Self::Output{
        /* conversion */
        num
    }
}