// This file is part of www.nand2tetris.org
// and the book "The Elements of Computing Systems"
// by Nisan and Schocken, MIT Press.
// File name: projects/8/ProgramFlow/BasicLoop/BasicLoop.vm

// Computes the sum 1 + 2 + ... + n and pushes the result onto
// the stack. The value n is given in argument[0], which must be 
// initialized by the caller of this code.

	push constant 0    
	pop local 0         // sum = 0
label LOOP
	push argument 0     
	push local 0
	add
	pop local 0	        // sum = sum + n
	push argument 0
	push constant 1
	sub
	pop argument 0      // n--
	push argument 0
	if-goto LOOP        // if n > 0, goto LOOP
	push local 0        // else, pushes sum to the stack's top