Macro define_measure_types 

macro_rules! define_measure_types {
    (
        $( $flag:ident )* ,

        $(
            scalar_properties [
                $(
                    $scalar_prop:ident [
                        $(
                            $scalar_unit:ident {
                                $($scalar_key:ident : $scalar_val:expr),* $(,)?
                            }
                        )*
                    ]
                )*
            ]
        )?

        $(
            vector_properties [
                $(
                    $vector_prop:ident [
                        $(
                            $vector_unit:ident {
                                $($vector_key:ident : $vector_val:expr),* $(,)?
                            }
                        )*
                    ]
                )*
            ]
        )?

        $(
            angle_measurement_units [
                $(
                    $angle_unit:ident {
                        $($angle_key:ident : $angle_val:expr),* $(,)?
                    }
                )*
            ]
        )?

        $(
            relationships [
                $(
                    $unit1:ident $dim1:tt == $unit2:ident $dim2:tt $op:tt $unit3:ident $dim3:tt $(,)?
                )*
            ]
        )?
    ) => { ... };
}