def eval(self, program):
"""Evaluate this program in a fresh environment with the prelude
already included. Returns the result of the last expression.
"""
# Fresh copy of the environment so tests don't interfere with one another.
env = Environment([Scope({})])
global_scope = self.env.scopes[0]
for key, value in global_scope.bindings.iteritems():
# We do a deep copy of mutable values.
if isinstance(value, List):
env.set(key, deepcopy(value))
elif isinstance(value, String):
env.set(key, deepcopy(value))
elif isinstance(value, Bytestring):
env.set(key, deepcopy(value))
else:
env.set(key, value)
parse_tree = parse(lex(program))
if isinstance(parse_tree, TrifleExceptionInstance):
self.fail("Parse error on: %r" % program)
result = NULL
for expression in parse_tree.values:
result = evaluate(expression, env)
if is_thrown_exception(result, error):
return result
return result
def evaluate_with_prelude(expression):
return evaluate(expression, env_with_prelude())
