/*
* Tail recursive and non-tail recursive 
* functions for computing sum of integers
* Note that this is kind of silly as Go does not have 
* tail recursion optimization
* @author gtowell
* created: Aug 1, 2021
*/
package main
import "fmt"

func main() {
	summ(10)
	summTR(10,0)
}

// not tail recursive version of sum
func summ(mx int) int {
	if (mx<=0) { return 0; }
	return mx + summ(mx-1);
}

//tail recursive version of sum
// this version is annoying because it requires the user to pass in tot
func summTR(mx int, tot int) int {
	if mx <=0 { return tot }
	return summTR(mx-1, tot+mx)
}

// summTR2 does tail recursion, but uses a private recursive function to do so!
// This gets past Go not alloing overloaded function names or default params!!
func summTR2(mx int) int {
	var ttr func(int, int) int // need to define the variable first so it is available for the recursion 
	ttr = func(mm int, tot int) int {
		if (mm<=0) { return tot }
		return ttr(mm-1, tot+mm)
	}
	return ttr(mx, 0)
}