Thickness[T] = tuple[l: T, t: T, r: T, b: T]

proc thickness(): Thickness[float] {...}{.raises: [], tags: [].}

proc thickness[T: Number](a: T; b: T; c: T; d: T): Thickness[T]

proc thickness[T: Number](a: T): Thickness[T]

proc thickness[T: Number](a: T; b: T): Thickness[T]

proc left[T: Number](self: Thickness[T]): T

proc top[T: Number](self: Thickness[T]): T

proc right[T: Number](self: Thickness[T]): T

proc bottom[T: Number](self: Thickness[T]): T

proc add[T: Number](self: Thickness[T]; other: Thickness[T]): Thickness[T]