Macro simple_units::combine_unit

macro_rules! combine_unit {
    ($unit1:ident, $per_unit1:ident, $unit2:ident, $per_unit2:ident, $unit1_unit2:ident, $unit1_per_unit2:ident, $unit2_per_unit1:ident, $per_unit1_unit2:ident) => { ... };
}

This macro combines two units and some permutation / inverse

Example:

init_unit!(Meter);
init_unit!(PerMeter);
init_unit!(Second);
init_unit!(PerSecond);
init_unit!(MeterSecond);
init_unit!(MeterPerSecond);
init_unit!(SecondPerMeter);
init_unit!(PerMeterSecond);
combine_unit!(Meter, PerMeter, Second, PerSecond, MeterSecond, MeterPerSecond, SecondPerMeter, PerMeterSecond);