Provides a concurrent safe iterator for generating bitstring combinations of given length.

bit_string_iterator.go

package hamming

// An asynchronous permutation Iterator for bitstrings
// So you want all the permuations of 3 bits choose 2 at a time? Well just
// create this async iterator which produces these bitstrings as there integer
// equivlent.
//
// bspIterator(3,2)
// 011 = 3
// 101 = 5
func bspIterator(n, k int) chan int64 {

	// Create buffer to pass integer of bitstring
	ch := make(chan int64, 0)

	// Recursive defintion
	switch {
	case k == 1:
		// This is the base case when asking for n choose one bit
		go func() {

			for i := 0; i < n; i++ {
				ch <- 1 << uint(i)
			}

			// Signal the consumer that the end is nigh
			close(ch)
		}()

	case k > 1:
		// The is the recursive step in which a logical or of every bit with
		// every permutation of n choose k-1 bits
		go func() {

			for i := range bspIterator(n, k-1) {
				for j := 0; j < n; j++ {

					// We test for equivlent permutations and throw it out
					if 1<<uint(j) != uint(i) {

						// A logical or with a lesser n choose k call will produce
						// all n choose k permutations
						ch <- 1<<uint(j) | i
					}
				}
			}

			// Signal the consumer that the end is nigh
			close(ch)
		}()
	}

	return ch
}