;; really simple calculator (add/subtract)
;; 

loop while run = true:
	src_in == get cli_opt(a);
		if cli_opt = '0' then FAIL
		else
			continue
	open_file(src_in) as #1
	
	read (#1):
		case of #1,1 :
			if ';;' then continue
			if "a" then var1 == "a"
		case of #1,2 :
			if ';;' then continue
			if "+" then x = '+'
			if "-" then x = '-'
		case of #1,3 :
			if ';;' then continue
			if "b" then var2 == "b"
	
	case of x:
		if x = '+' then solution == var1 + var2
		if x = '-' then solution == var1 - var2
		else
			FAIL
	
	display solution