Function range_step_from 

pub fn range_step_from<A>(start: A, step: A) -> RangeStepFrom<A> 
where
    A: Add<A, Output = A> + Clone,

Return an iterator over the infinite range starting at start and continuing forever by step.

Note: Currently, the Iterator implementation is not checked for overflow. If you use a finite-sized integer type and the integer overflows, it might panic in debug mode or wrap around in release mode. This behavior is not guaranteed and may change at any time.