expad.go

func expand(s string, f func(string) string) string {
	if len(s) < len(FOO) {
		return s
	}
	for i := strings.Index(s, FOO); i != -1; i = strings.Index(s, FOO){
		t := s[:i]
		t = t + f(s[i+1:i+len(FOO)])
		t = t + s[i+len(FOO):]
		s = t
	}
	return s
}

What I want is a C-style while loop but when I run it as for i := strings.Index(s, FOO) {} it gives a compilation error saying the function is used as a value.