def create_root_symbols(self):
"""Insert magical symbols above the root of the grammar in
order to match the beginning and end of the sample."""
RootSymbol = Symbol(Token(None,None,'R00t.Symbol'))
RootSymbol.GlobalSymbolDict=self.GlobalSymbolDict
StartDocSymbol = Symbol(Token(None,None,'%^'))
StartDocSymbol.regex = Set('%^')
StartDocSymbol.is_lit = True
StartDocSymbol.GlobalSymbolDict=self.GlobalSymbolDict
EndDocSymbol = Symbol(Token(None,None,'%$'))
EndDocSymbol.regex = Set('%$')
EndDocSymbol.is_lit = True
EndDocSymbol.GlobalSymbolDict=self.GlobalSymbolDict
RootSymbol.productions = [Production(RootSymbol,[StartDocSymbol]+self.get_roots()+[EndDocSymbol])]
self.GlobalSymbolDict['R00t.Symbol'] = RootSymbol #XXX this is a nasty hack
self.GlobalSymbolDict['%^']=StartDocSymbol
self.GlobalSymbolDict['%$']=EndDocSymbol
def parse_cst(self):
"""Given that the token generator is positioned at the start
of the concrete grammar, read rules. After this routine
completes, each symbol in the GlobalSymbolDict has a set of
productions that contain Tokens, not symbols. Conversion from
tokens to symbols happens in promote_productions."""
stack = []
self.tokenizer.next().must_be('{')
for token in self.tokenizer:
stack += [ token ] # Build a stack to process
if token.text == ".":
# We've got a rule to process. Start by determining correct syntax.
stack[1].must_be(':')
## Name analysis
stack[0].assert_symbol_name()
production_elements = stack[2:-1]
for element in production_elements:
element.assert_symbol_name()
if stack[0].text in self.GlobalSymbolDict: # Redefined lexical sym or add a new production?
existingSymbol = self.GlobalSymbolDict[stack[0].text]
if existingSymbol.is_gla:
raise Exception("Lexical Symbol %s redefined at %d,%d. Originally at %d,%d" % \
(stack[0].text, stack[0].line, stack[0].col, \
existingSymbol.defining_token.line, existingSymbol.defining_token.col))
existingSymbol.productions += [Production(existingSymbol,production_elements)]
else: # Brand new symbol occurrence
s = Symbol(stack[0])
s.is_gla = False
s.productions = [Production(s,production_elements)]
self.GlobalSymbolDict[stack[0].text] = s
stack = []
elif token.text == "{":
raise Exception("Unexpected %s" % token)
elif token.text == "}":
if len(stack) > 1: raise Exception("Unfinished lexical specification beginning with %s" % stack[0])
#pp = pprint.PrettyPrinter()
#pp.pprint(self.GlobalSymbolDict)
return
else: pass
