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from rpython.rlib.parsing.lexer import Token, SourcePos
from rpython.rlib.parsing.parsing import *
class EvaluateVisitor(object):
def visit_additive(self, node):
if len(node.children) == 1:
return node.children[0].visit(self)
else:
return node.children[0].visit(self) + node.children[2].visit(self)
def visit_multitive(self, node):
if len(node.children) == 1:
return node.children[0].visit(self)
else:
return node.children[0].visit(self) * node.children[2].visit(self)
def visit_primary(self, node):
if len(node.children) == 1:
return node.children[0].visit(self)
else:
return node.children[1].visit(self)
def visit_decimal(self, node):
return int(node.children[0].symbol)
def test_simple_packrat():
class ToAstVisistor(object):
def visit_additive(self, node):
if len(node.children) == 1:
return node.children[0].visit(self)
return Nonterminal(
"additive", [node.children[0].visit(self),
node.children[2].visit(self)])
def visit_multitive(self, node):
if len(node.children) == 1:
return node.children[0].visit(self)
return Nonterminal(
"multitive", [node.children[0].visit(self),
node.children[2].visit(self)])
def visit_primary(self, node):
if len(node.children) == 1:
return node.children[0].visit(self)
return node.children[1].visit(self)
def visit_decimal(self, node):
return Nonterminal(
"decimal",
[Symbol(int(node.children[0].symbol), "", None)])
r1 = Rule("additive", [["multitive", "+", "additive"], ["multitive"]])
r2 = Rule("multitive", [["primary", "*", "multitive"], ["primary"]])
r3 = Rule("primary", [["(", "additive", ")"], ["decimal"]])
r4 = Rule("decimal", [[symb] for symb in "0123456789"])
p = PackratParser([r1, r2, r3, r4], "additive")
print p.parse([Token(c, c, SourcePos(i, 0, i)) for i, c in enumerate("2*(3+4)")])
tree = p.parse([Token(c, c, SourcePos(i, 0, i)) for i, c in enumerate("2*2*2*(7*3+4+5*6)")])
ast = tree.visit(ToAstVisistor())
tree = p.parse([Token(c, c, SourcePos(i, 0, i)) for i, c in enumerate("2*(3+4)")])
r = tree.visit(EvaluateVisitor())
assert r == 14
tree = p.parse([Token(c, c, SourcePos(i, 0, i)) for i, c in enumerate("2*(3+5*2*(2+6))")])
print tree
r = tree.visit(EvaluateVisitor())
assert r == 166
def test_bad():
r1 = Rule("S", [["x", "S", "x"], ["x"]])
p = PackratParser([r1], "S")
assert p.parse([Token(c, c, SourcePos(i, 0, i)) for i, c in enumerate("xxxxxxxxxxxxxxx")]) is not None
def test_leftrecursion_detection():
r1 = Rule("A", [["A"]])
py.test.raises(AssertionError, PackratParser, [r1], "A")
r1 = Rule("A", [["B"]])
r2 = Rule("B", [["A"]])
py.test.raises(AssertionError, PackratParser, [r1, r2], "B")
def test_epsilon():
r1 = Rule("S", [["x", "S", "x"], ["y"], []])
p = PackratParser([r1], "S")
assert p.parse([Token(c, i, SourcePos(i, 0, i))
for i, c, in enumerate("xyx")]) is not None
assert p.parse([Token(c, i, SourcePos(i, 0, i))
for i, c, in enumerate("xx")]) is not None
t = p.parse([Token(c, i, SourcePos(i, 0, i))
for i, c, in enumerate("xxxxxx")])
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