def _abbreviation(self):
self._match(tokens.QUOTE)
if self._lookahead_type(0) == tokens.LPAREN:
expr = self._list()
else:
expr = self._simple_datum()
return Pair(Symbol('quote'), Pair(expr, EmptyList))
def _simple_datum(self):
token = self._lookahead_token(0)
if token.type == tokens.NUMBER:
expr = Number(int(token.text))
elif token.type == tokens.BOOLEAN:
expr = Boolean(True if token.text == '#t' else False)
elif token.type == tokens.CHARACTER:
expr = Character(token.text[2:])
elif token.type == tokens.STRING:
expr = String(token.text.strip('"'))
elif token.type == tokens.ID:
expr = Symbol(token.text)
else:
raise ParserException('No viable alternative')
self._match(token.type)
return expr
def is_assignment(expr):
return is_tagged_list(expr, Symbol('set!'))
def make_begin(seq):
return cons(Symbol('begin'), seq)
def is_load(expr):
return is_tagged_list(expr, Symbol('load'))
def make_procedure(params, body, env):
return cons(Symbol('procedure'),
cons(params, cons(body, cons(env, EmptyList))))
def is_primitive_procedure(expr):
return is_tagged_list(expr, Symbol('primitive'))
def make_if(predicate, consequent, alternative):
return tolist(Symbol('if'), predicate, consequent, alternative)
def is_or(expr):
return is_tagged_list(expr, Symbol('or'))
def is_let_binding(expr):
return is_tagged_list(expr, Symbol('set'))
def is_if(expr):
return is_tagged_list(expr, Symbol('if'))
def is_quoted(expr):
return is_tagged_list(expr, Symbol('quote'))
def make_lambda(params, body):
return cons(Symbol('lambda'), cons(params, body))
def is_lambda(expr):
return is_tagged_list(expr, Symbol('lambda'))
def _eval_definition(self, expr, env):
define_variable(
definition.definition_variable(expr),
self._eval(definition.definition_value(expr), env),
env)
return Symbol('ok')
def is_cond(expr):
return is_tagged_list(expr, Symbol('cond'))
def _eval_assignment(self, expr, env):
env.set_variable_value(
assignment.assignment_variable(expr),
self._eval(assignment.assignment_value(expr), env))
return Symbol('ok')
def is_cond_else_clause(clause):
return cond_predicate(clause) == Symbol('else')
def is_compound_procedure(expr):
return is_tagged_list(expr, Symbol('procedure'))
def is_definition(expr):
return is_tagged_list(expr, Symbol('define'))
def primitive_procedure_values():
return [Pair(Symbol('primitive'), Pair(proc, EmptyList))
for _, proc in BUILTIN_PROCEDURES]
def is_begin(expr):
return is_tagged_list(expr, Symbol('begin'))
