class Syntax(object):
'''See the __init__ method.'''
def __init__(self, start_symbol, terminals=None):
'''Creates the syntax of some language which grammar is defined
by the calls to the methods of this class.
It is a high level view of the class Grammar which provides
a much more rich and high level expressions.
The parameters 'start_symbol' and 'terminals' are the same
parameters of the constructor of Grammar, but a difference of Grammar,
the 'start_symbol' is an required element.
See the documentation of Grammar.
'''
if start_symbol is None:
raise ValueError("The parameter 'start_symbol' must not be None.")
self._grammar = Grammar(start_symbol, terminals)
@staticmethod
def _symbols(symbols, sym_production=None):
'''Utility to make 'symbols' a tuple, concatenated with 'sym_production'
if it is not None.
'''
if not isinstance(symbols, (list, tuple)):
symbols = (str(symbols), )
if sym_production:
return tuple(symbols) + (sym_production, )
else:
return tuple(symbols)
def terminal(self, terminal, _unused):
'''Adds a terminal element.
See the documentation of 'add_terminal' of Grammar.
'''
self._grammar.add_terminal(terminal)
return terminal
def rule(self, symbols, production_name):
'''Adds a rule 'production_name' -> 'symbols'.
See the documentation of 'add_production' of Grammar.
'''
self._grammar.add_rule(production_name, self._symbols(symbols))
return production_name
def choice(self, alternatives, production_name):
'''Adds multiples rules, each rule assigned to the same 'production_name'
symbol, making each one a possible alternative.
See the documentation of 'add_rule' of Grammar.
'''
if len(alternatives) <= 1:
raise ValueError('''Expected two or more alternatives,
but received '%s'.''' % str(alternatives))
for alternative in alternatives:
self._grammar.add_rule(production_name, self._symbols(alternative))
return production_name
def repeat(self, symbols, production_name):
'''Adds a high level rule which derivates in "one or more" times
the 'production_name' symbol.'''
self._grammar.add_rule(production_name,
self._symbols(symbols, production_name))
self._grammar.add_rule(production_name, self._symbols(symbols))
return production_name
def optional(self, symbols, production_name):
'''Adds a high level rule which derivates in "zero or one" times
the 'production_name' symbol.'''
self._grammar.add_rule(production_name, self._symbols(symbols))
self._grammar.add_empty(production_name)
return production_name
def as_grammar(self):
'''Returns a grammar.'''
return self._grammar
class Syntax(object):
'''See the __init__ method.'''
def __init__(self, start_symbol, terminals = None):
'''Creates the syntax of some language which grammar is defined
by the calls to the methods of this class.
It is a high level view of the class Grammar which provides
a much more rich and high level expressions.
The parameters 'start_symbol' and 'terminals' are the same
parameters of the constructor of Grammar, but a difference of Grammar,
the 'start_symbol' is an required element.
See the documentation of Grammar.
'''
if start_symbol is None:
raise ValueError("The parameter 'start_symbol' must not be None.")
self._grammar = Grammar(start_symbol, terminals)
@staticmethod
def _symbols(symbols, sym_production=None):
'''Utility to make 'symbols' a tuple, concatenated with 'sym_production'
if it is not None.
'''
if not isinstance(symbols, (list, tuple)):
symbols = (str(symbols), )
if sym_production:
return tuple(symbols)+(sym_production,)
else:
return tuple(symbols)
def terminal(self, terminal, _unused):
'''Adds a terminal element.
See the documentation of 'add_terminal' of Grammar.
'''
self._grammar.add_terminal(terminal)
return terminal
def rule(self, symbols, production_name):
'''Adds a rule 'production_name' -> 'symbols'.
See the documentation of 'add_production' of Grammar.
'''
self._grammar.add_rule(production_name, self._symbols(symbols))
return production_name
def choice(self, alternatives, production_name):
'''Adds multiples rules, each rule assigned to the same 'production_name'
symbol, making each one a possible alternative.
See the documentation of 'add_rule' of Grammar.
'''
if len(alternatives) <= 1:
raise ValueError('''Expected two or more alternatives,
but received '%s'.''' % str(alternatives))
for alternative in alternatives:
self._grammar.add_rule(production_name,
self._symbols(alternative))
return production_name
def repeat(self, symbols, production_name):
'''Adds a high level rule which derivates in "one or more" times
the 'production_name' symbol.'''
self._grammar.add_rule(production_name,
self._symbols(symbols, production_name))
self._grammar.add_rule(production_name,
self._symbols(symbols))
return production_name
def optional(self, symbols, production_name):
'''Adds a high level rule which derivates in "zero or one" times
the 'production_name' symbol.'''
self._grammar.add_rule(production_name, self._symbols(symbols))
self._grammar.add_empty(production_name)
return production_name
def as_grammar(self):
'''Returns a grammar.'''
return self._grammar
