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arpeggio-gm
Commit 6c12636c authored by Igor Dejanovic's avatar Igor Dejanovic
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bugfix in backtracking

parent 913ce9a6
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Showing with 84 additions and 41 deletions
arpeggio/__init__.py
View file @ 6c12636c
......@@ -151,38 +151,47 @@ class ParsingExpression(object):
def _parse_intro(self, parser):
if parser.debug:
print("Parsing {}".format(self.name))
print(">> Entering rule {}".format(self.name))
# Skip whitespaces if we are not in the lexical rule
if not parser._in_lex_rule:
parser._skip_ws()
# Set the begining position in the input stream of
# this parsing expression
self.c_pos = parser.position
# # Set the beginning position in the input stream of
# # this parsing expression
# self.c_pos = parser.position
def parse(self, parser):
self._parse_intro(parser)
# Current position could change in recursive calls
# so save it.
c_pos = self.c_pos
c_pos = parser.position
# Memoization.
# If this position is already parsed by this parser expression use
# the result
if c_pos in self.result_cache:
if parser.debug:
print("Result for [{}, {}] founded in result_cache.".format(self, self.c_pos))
result, new_pos = self.result_cache[c_pos]
parser.position = new_pos
if parser.debug:
print("** Cache hit for [{}, {}] = '{}'".format(self.name, c_pos, unicode(result)))
if parser.debug:
print("<< Leaving rule {}".format(self.name))
return result
# We are descending down
if parser.nm:
parser.nm._up = False
result = self._parse(parser)
try:
result = self._parse(parser)
except NoMatch:
parser.position = c_pos # Backtracking
raise
finally:
if parser.debug:
print("<< Leaving rule {}".format(self.name))
# Create terminal or non-terminal if result is not
# already a Terminal.
......@@ -211,7 +220,7 @@ class ParsingExpression(object):
Used to report most generic language element expected at the
place of the NoMatch exception.
"""
if self.root and self.c_pos == nm.position and nm._up:
if self.root and parser.position == nm.position and nm._up:
nm.rule = self.rule
......@@ -227,6 +236,7 @@ class Sequence(ParsingExpression):
if result:
results.append(result)
except NoMatch as m:
# parser.position = self.c_pos # Backtracking
self._nm_change_rule(m, parser)
raise
......@@ -241,12 +251,13 @@ class OrderedChoice(Sequence):
def _parse(self, parser):
result = None
match = False
c_pos = parser.position
for e in self.nodes:
try:
result = e.parse(parser)
match = True
except NoMatch as m:
parser.position = self.c_pos # Backtracking
parser.position = c_pos # Backtracking
self._nm_change_rule(m, parser)
else:
break
......@@ -269,10 +280,11 @@ class Optional(Repetition):
"""
def _parse(self, parser):
result = None
c_pos = parser.position
try:
result = self.nodes[0].parse(parser)
except NoMatch:
parser.position = self.c_pos # Backtracking
parser.position = c_pos # Backtracking
return result
......@@ -286,10 +298,10 @@ class ZeroOrMore(Repetition):
results = []
while True:
try:
self.c_pos = parser.position
c_pos = parser.position
results.append(self.nodes[0].parse(parser))
except NoMatch:
parser.position = self.c_pos # Backtracking
parser.position = c_pos # Backtracking
break
return results
......@@ -304,11 +316,11 @@ class OneOrMore(Repetition):
first = False
while True:
try:
self.c_pos = parser.position
c_pos = parser.position
results.append(self.nodes[0].parse(parser))
first = True
except NoMatch:
parser.position = self.c_pos # Backtracking
parser.position = c_pos # Backtracking
if not first:
raise
break
......@@ -323,19 +335,21 @@ class SyntaxPredicate(ParsingExpression):
consume any input.
"""
class And(SyntaxPredicate):
"""
This predicate will succeed if the specified expression matches current
input.
"""
def _parse(self, parser):
c_pos = parser.position
for e in self.nodes:
try:
e.parse(parser)
except NoMatch:
parser.position = self.c_pos
parser.position = c_pos
raise
parser.position = self.c_pos
parser.position = c_pos
class Not(SyntaxPredicate):
......@@ -344,14 +358,15 @@ class Not(SyntaxPredicate):
current input.
"""
def _parse(self, parser):
c_pos = parser.position
for e in self.nodes:
try:
e.parse(parser)
except NoMatch:
parser.position = self.c_pos
parser.position = c_pos
return
parser.position = self.c_pos
parser._nm_raise(self.name, self.c_pos, parser)
parser.position = c_pos
parser._nm_raise(self.name, c_pos, parser)
class Empty(SyntaxPredicate):
......@@ -382,7 +397,7 @@ class Combine(Decorator):
old_in_lex_rule = parser._in_lex_rule
parser._in_lex_rule = True
self.c_pos = parser.position
c_pos = parser.position
try:
for parser_model_node in self.nodes:
results.append(parser_model_node.parse(parser))
......@@ -390,10 +405,10 @@ class Combine(Decorator):
results = flatten(results)
# Create terminal from result
return Terminal(self.rule if self.root else '', self.c_pos, \
return Terminal(self.rule if self.root else '', c_pos, \
"".join([str(result) for result in results]))
except NoMatch:
parser.position = self.c_pos # Backtracking
parser.position = c_pos # Backtracking
raise
finally:
parser._in_lex_rule = old_in_lex_rule
......@@ -411,11 +426,13 @@ class Match(ParsingExpression):
@property
def name(self):
return "%s(%s)" % (self.__class__.__name__, self.to_match)
def parse(self, parser):
self._parse_intro(parser)
if parser._in_parse_comment:
return self._parse(parser)
c_pos = parser.position
comments = []
try:
......@@ -434,7 +451,7 @@ class Match(ParsingExpression):
# If comment match successfull try terminal match again
if comments:
match = self._parse(parser)
match.comments = NonTerminal('comment', self.c_pos,
match.comments = NonTerminal('comment', c_pos,
comments)
else:
parser._nm_raise(nm)
......@@ -464,17 +481,19 @@ class RegExMatch(Match):
self.regex = re.compile(to_match)
def _parse(self, parser):
m = self.regex.match(parser.input[parser.position:])
c_pos = parser.position
m = self.regex.match(parser.input[c_pos:])
if m:
parser.position += len(m.group())
if parser.debug:
print("Match {} at {}".format(m.group(), self.c_pos))
return Terminal(self.rule if self.root else '', self.c_pos,
print("++ Match '%s' at %d => '%s'" % (m.group(), \
c_pos, parser.context(len(m.group()))))
parser.position += len(m.group())
return Terminal(self.rule if self.root else '', c_pos,
m.group())
else:
if parser.debug:
print("NoMatch at {}".format(self.c_pos))
parser._nm_raise(self.name, self.c_pos, parser)
print("-- NoMatch at {}".format(c_pos))
parser._nm_raise(self.name, c_pos, parser)
class StrMatch(Match):
......@@ -489,16 +508,18 @@ class StrMatch(Match):
self.to_match = to_match
def _parse(self, parser):
if parser.input[parser.position:].startswith(self.to_match):
parser.position += len(self.to_match)
c_pos = parser.position
if parser.input[c_pos:].startswith(self.to_match):
if parser.debug:
print("Match {} at {}".format(self.to_match, self.c_pos))
return Terminal(self.rule if self.root else '', self.c_pos,
print("++ Match '{}' at {} => '{}'".format(self.to_match,\
c_pos, parser.context(len(self.to_match))))
parser.position += len(self.to_match)
return Terminal(self.rule if self.root else '', c_pos,
self.to_match)
else:
if parser.debug:
print("NoMatch at {}".format(self.c_pos))
parser._nm_raise(self.to_match, self.c_pos, parser)
print("-- NoMatch at {}".format(c_pos))
parser._nm_raise(self.to_match, c_pos, parser)
def __str__(self):
return self.to_match
......@@ -535,12 +556,13 @@ class EndOfFile(Match):
return "EOF"
def _parse(self, parser):
if len(parser.input) == parser.position:
return Terminal('EOF', self.c_pos, '')
c_pos = parser.position
if len(parser.input) == c_pos:
return Terminal('** EOF', c_pos, '')
else:
if parser.debug:
print("EOF not matched.")
parser._nm_raise(self.name, self.c_pos, parser)
print("!! EOF not matched.")
parser._nm_raise(self.name, c_pos, parser)
def EOF(): return EndOfFile()
......@@ -796,6 +818,27 @@ class Parser(object):
if self.input[self.line_ends[line - 1]] in '\n\r':
col -= 1
return line + 1, col + 1
def context(self, length=None, position=None):
"""
Returns current context substring, i.e. the substring around current
position.
Args:
length(int): If given used to mark with asterisk a length chars from
current position.
position(int): The position in the input stream.
"""
if not position:
position = self.position
if length:
return "{}*{}*{}".format(
str(self.input[max(position - 10, 0):position]),
str(self.input[position:position + length]),
str(self.input[position + length:position+10]))
else:
return "{}*{}".format(
str(self.input[max(position - 10, 0):position]),
str(self.input[position:position + 10]))
def _skip_ws(self):
"""
......
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