dimensioned::make_units!

macro_rules! make_units { ($System:ident, $allowed_root:ident; base { $($Type:ident, $constant:ident, $print_as:ident;)* } derived {$($Derived:ident($derived_constant: ident) = $e: expr;    )*} ) => (
    #[derive(Copy, Clone)]
    pub struct $System<$($Type: Peano),*> {
        $($constant: PhantomData<$Type>),*
    }
    impl<$($Type: Peano),*> Dimension for $System<$($Type),*> {}

    // using $Type and $constant for these traits is confusing. It should really be $Type_Left and
    // $Type_Right or something, but as far as I can tell, that is not supported by Rust
    #[allow(non_camel_case_types)]
    impl<$($Type),*, $($constant),*> KeepDim<$System<$($constant),*>> for $System<$($Type),*> where
        $($Type: Peano + KeepPeano<$constant>),*, $($constant: Peano),* {
            type Output = $System<$(<$Type as KeepPeano<$constant>>::Output),*>;
        }
    #[allow(non_camel_case_types)]
    impl<$($Type),*, $($constant),*> AddDim<$System<$($constant),*>> for $System<$($Type),*> where
        $($Type: Peano + AddPeano<$constant>),*, $($constant: Peano),* {
            type Output = $System<$(<$Type as AddPeano<$constant>>::Output),*>;
        }
    #[allow(non_camel_case_types)]
    impl<$($Type),*, $($constant),*> SubDim<$System<$($constant),*>> for $System<$($Type),*> where
        $($Type: Peano + SubPeano<$constant>),*, $($constant: Peano),* {
            type Output = $System<$(<$Type as SubPeano<$constant>>::Output),*>;
        }
    impl<$($Type),*, RHS> MulDim<RHS> for $System<$($Type),*> where
        $($Type: Peano + MulPeano<RHS>),*, RHS: Peano {
            type Output = $System<$(<$Type as MulPeano<RHS>>::Output),*>;
        }
    impl<$($Type),*, RHS> DivDim<RHS> for $System<$($Type),*> where
        $($Type: Peano + DivPeano<RHS>),*, RHS: Peano {
            type Output = $System<$(<$Type as DivPeano<RHS>>::Output),*>;
        }
    impl<$($Type),*> NegDim for $System<$($Type),*> where
        $($Type: Peano + Negate),* {
            type Output = $System<$(<$Type as Negate>::Output),*>;
        }

    impl<$($Type),*> DimToString for $System<$($Type),*>
        where $($Type: ToInt),* {
            fn to_string() -> String {
                let mut _string = String::new();
                $(
                    let temp = match <$Type as ToInt>::to_int() {
                        0 => ("", "".to_string()),
                        1 => (stringify!($print_as), "*".to_string()),
                        _power => (stringify!($print_as), format!("^{}*", _power/<$allowed_root as ToInt>::to_int()))
                    };
                    _string = format!("{}{}{}", _string, temp.0, temp.1);
                )*
                _string.pop();
                _string
            }
        }

    __make_types!($System, $allowed_root | $($Type),* | $($Type),* |);
    // fixme: when __make_types is fixed, use following line to call:
    // __make_types!($System, $allowed_root | $($Type),* | $($Type),*);

    #[allow(non_upper_case_globals)]
    pub const one: Dim<Unitless, f64> = Dim(1.0, PhantomData);
    $(#[allow(non_upper_case_globals)] pub const $constant: Dim<$Type, f64> = Dim(1.0, PhantomData);)*

        // $(
        //   __make_derived_type!($Derived, $e);
        //   pub const $derived_constant: Dim<$Derived, f64> = Dim(1.0, PhantomData);
        //   )*
        );
}