Function rect_iter::gen_rect_conv

pub fn gen_rect_conv<D, T, U, I, J>(
    source: &impl Get2D<Item = T>, 
    gen_dist: impl Fn() -> D, 
    source_range: RectRange<I>, 
    dest_range: RectRange<J>, 
    convert: impl Fn(&T) -> U
) -> Result<D, IndexError> where
    D: GetMut2D<Item = U> + Default,
    T: Clone,
    I: Num + PartialOrd + ToPrimitive + Copy,
    J: Num + PartialOrd + ToPrimitive + Copy,