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#######################################################################
# Name: robot.py
# Purpose: Simple DSL for defining robot movement.
# Author: Igor R. Dejanovic <igor DOT dejanovic AT gmail DOT com>
# Copyright: (c) 2011-2014 Igor R. Dejanovic <igor DOT dejanovic AT gmail DOT com>
# License: MIT License
#
# This example is inspired by an example from LISA tool (http://labraj.uni-mb.si/lisa/)
# presented during the lecture given by prof. Marjan Mernik (http://lpm.uni-mb.si/mernik/)
# at the University of Novi Sad in June, 2011.
#
# An example of the robot program:
# begin
# up
# up
# left
# down
# right
# end
#######################################################################
from __future__ import print_function, unicode_literals
import os
from arpeggio import ZeroOrMore, EOF, PTNodeVisitor, ParserPython, \
visit_parse_tree
from arpeggio.export import PMDOTExporter, PTDOTExporter
# Grammar rules
def robot(): return 'begin', ZeroOrMore(command), 'end', EOF
def command(): return [UP, DOWN, LEFT, RIGHT]
def UP(): return 'up'
def DOWN(): return 'down'
def LEFT(): return 'left'
def RIGHT(): return 'right'
# Semantic actions visitor
class RobotVisitor(PTNodeVisitor):
def visit_robot(self, node, children):
if self.debug:
print("Evaluating position")
position = [0, 0]
for move in children:
position[0] += move[0]
position[1] += move[1]
return position
def visit_command(self, node, children):
if self.debug:
print("Command")
return children[0]
def visit_UP(self, node, children):
if self.debug:
print("Going up")
return (0, 1)
def visit_DOWN(self, node, children):
if self.debug:
print("Going down")
return (0, -1)
def visit_LEFT(self, node, children):
if self.debug:
print("Going left")
return (-1, 0)
def visit_RIGHT(self, node, children):
if self.debug:
print("Going right")
return (1, 0)
def main(debug=False):
# Load program
current_dir = os.path.dirname(__file__)
input_program = open(os.path.join(current_dir, 'program.rbt'), 'r').read()
# First we will make a parser - an instance of the robot parser model.
# Parser model is given in the form of python constructs therefore we
# are using ParserPython class.
parser = ParserPython(robot, debug=debug)
# We create a parse tree out of textual input
parse_tree = parser.parse(input_program)
# visit_parse_tree will start semantic analysis.
# In this case semantic analysis will evaluate expression and
# returned value will be the final position of the robot.
result = visit_parse_tree(parse_tree, RobotVisitor(debug=debug))
if debug:
print("position = ", result)
if __name__ == "__main__":
# In debug mode dot (graphviz) files for parser model
# and parse tree will be created for visualization.
# Checkout current folder for .dot files.
main(debug=True)
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