#!/usr/local/bin/vtml -2 -b_ -spass_first -S

##echo This script adds two numbers.  The format of the tape is:
##echo
##echo	_1...1_1...1_
##echo
##echo where 1...1 is a string of 1s.  The first string of 1s represents the
##echo first number in unary, i.e., the number n is represented by a string of
##echo (n + 1) 1s (e.g. 2 is represented by `111').  The second string of 1s
##echo represents the second number in unary.  The `_' in the middle separates 
##echo the numbers.  So an initial tape of `_111_111_' will add 2 and 2, and 
##echo hopefully get `_11111___' (`11111' is 4 in unary).
##echo

pass_first, 1, pass_first, 1, R		# get past the first number
pass_first, _, pass_second, 1, R	# change the middle _
pass_second, 1, pass_second, 1, R	# get past the second number
pass_second, _, delete1, _, L		# end of second number, start going 
					# back to delete the last 1

delete1, 1, delete2, _, L  	# delete the last 1, go back to 
				# delete the second to last 1

delete2, 1, HALT, _, R		# deletes the second to last 1