use num::Float;

struct MulIter<I>
where
    I: Iterator,
{
    iter: I,
    scalar: I::Item,
}

impl<I> MulIter<I>
where
    I: Iterator,
    I::Item: Float,
{
    pub fn new(iter: I, scalar: I::Item) -> MulIter<I> {
        MulIter {
            iter,
            scalar,
        }
    }
}

impl<I> Iterator for MulIter<I>
where
    I: Iterator,
    I::Item: Float,
{
    type Item = I::Item;

    fn next(&mut self) -> Option<Self::Item> {
        match self.iter.next() {
            Some(value) => Some(value * self.scalar),
            None => None,
        }
    }
}