range.go

package loop

// Range creates a function iterator to iterate between two given
// integer like values.
//
// The first argument is the starting value, which is included in the
// iteration. The second argument is the stop value, which is when the
// iteration is stopped. This value is not included.
//
// This function is basically loop.RangeWithStep(start, stop, 1)
func Range[Int intType](start Int, stop Int) func(func(Int) bool) {
	return RangeWithStep(start, stop, 1)
}

// RangeWithStep creates a function iterator to iterate between two values
// with a given step incrementor.
//
// The first value is always returned (provided the stop value is value for
// the step amount)
// The stop value is not included.
// The step value can be either either greater than or less than 0. If the
// step is 0 then no iteration will take place.
func RangeWithStep[Int intType](start Int, stop Int, step Int) func(func(Int) bool) {
	return func(yield func(Int) bool) {
		if step == 0 {
			return
		}

		delta := int64(stop) - int64(start)
		steps := int64(delta) / int64(step)
		rem := int64(delta) % int64(step)
		if rem > 0 {
			steps += 1
		}

		for i := int64(0); i < steps; i++ {
			num := i*int64(step) + int64(start)
			if !yield(Int(num)) {
				return
			}
		}
	}
}