jseteny / fileman-go-fp

fileman-go-fp

You can find the following functional programming concepts in the code.

Partial Application

The following function implements the Partial Application functional programming concept. In this case it makes it possible to optimize out the unnecessary strings.ReplaceAll() calls.

See the benchmark results here: (https://github.com/jseteny/fileman-fp-go/blob/master/image.jpg?raw=true)

Please see https://en.wikipedia.org/wiki/Partial_application

func makeCalcList(path string) func(dirs []string) []string {
	exp := strings.ReplaceAll(path, "/", ".*/.*")

	return func(dirs []string) []string {
		result := make([]string, 0)
		for _, dir := range dirs {
			ok, err := regexp.MatchString(exp, dir)
			if err != nil {
				panic(err)
			}
			if ok {
				result = append(result, dir)
			}
		}
		return result
	}
}

You can use it in an optimised way doing the Partial Application outside the loop and calling the Partially Applied function inside the loop.

func BenchmarkFindPathOptimized(t *testing.B) {
	calcList := makeCalcList("a/o")
	for n := 0; n < t.N; n++ {
		calcList(dirs)
	}
}

or using the following short hand form

func BenchmarkFindPath(t *testing.B) {
	for n := 0; n < t.N; n++ {
		makeCalcList("a/o")(dirs)
	}
}