def visit_class_stmt(self, stmt: Class):
superclass = None
if stmt.superclass is not None:
superclass = self._evaluate(stmt.superclass)
if not isinstance(superclass, YaploxClass):
raise YaploxRuntimeError(stmt.superclass.name,
"Superclass must be a class.")
self.environment.define(stmt.name.lexeme, None)
if stmt.superclass is not None:
self.environment = Environment(self.environment)
self.environment.define("super", superclass)
methods: Dict[str, YaploxFunction] = {}
for method in stmt.methods:
function = YaploxFunction(method, self.environment,
method.name.lexeme == "init")
methods[method.name.lexeme] = function
klass = YaploxClass(name=stmt.name.lexeme,
superclass=superclass,
methods=methods)
if stmt.superclass is not None:
self.environment = self.environment.enclosing # type: ignore
self.environment.assign(stmt.name, klass)
def call(self, interpreter, arguments):
environment = Environment(self.closure)
for declared_token, argument in zip(self.declaration.params,
arguments):
environment.define(declared_token.lexeme, argument)
try:
interpreter.execute_block(self.declaration.body, environment)
except YaploxReturnException as yaplox_return:
if self.is_initializer:
# When we're in init(), return this as an early return
return self.closure.get_at(0, "this")
return yaplox_return.value
if self.is_initializer:
# When init() is called directly on a class
return self.closure.get_at(0, "this")
def test_falsy_values(self, create_token_factory, falsy_values):
# Set a key with the value 0.0.
# In python this is evaluated as false, but we want this value back!
env = Environment()
foo_token = create_token_factory(token_type=TokenType.VAR,
lexeme="Foo")
env.define("Foo", falsy_values)
if isinstance(falsy_values, bool):
assert env.get(foo_token) is falsy_values
else:
assert env.get(foo_token) == falsy_values
def bind(self, instance: YaploxInstance) -> YaploxFunction:
environment = Environment(self.closure)
environment.define("this", instance)
return YaploxFunction(self.declaration, environment,
self.is_initializer)
def __init__(self):
self.globals = Environment()
self.environment = self.globals
self.locals = dict()
self.globals.define("clock", Clock())
class Interpreter(ExprVisitor, StmtVisitor):
def __init__(self):
self.globals = Environment()
self.environment = self.globals
self.locals = dict()
self.globals.define("clock", Clock())
def interpret(self, statements: List[Stmt], on_error=None) -> Any:
try:
res = None
for statement in statements:
logger.debug("Executing", statement=statement)
res = self._execute(statement)
# The return in the interpreter is not default Lox. It's added for now
# to make testing and debugging easier.
return res
except YaploxRuntimeError as excp:
on_error(excp)
def _execute(self, stmt: Stmt):
return stmt.accept(self)
def resolve(self, expr: Expr, depth: int):
self.locals[expr] = depth
@staticmethod
def _stringify(obj) -> str:
if obj is None:
return "nil"
if isinstance(obj, float):
# Print floats and remove trailing zero's, and if the dot is at the right
# part, remove it too. Decimal precision is set to 6 positions
return f"{obj:0.6f}".rstrip("0").rstrip(".")
return str(obj)
@staticmethod
def _binary_plus(expr, left, right):
if isinstance(left, (float, int)) and isinstance(right, (float, int)):
return left + right
if isinstance(left, str) and isinstance(right, str):
return str(left + right)
raise YaploxRuntimeError(
expr.operator, "Operands must be two numbers or two strings")
@staticmethod
def _is_equal(a, b) -> bool:
if a is None and b is None:
return True
if a is None:
return False
return a == b
def visit_binary_expr(self, expr: Binary):
left = self._evaluate(expr.left)
right = self._evaluate(expr.right)
token_type = expr.operator.token_type
# Validate that for the following Tokens the operands are numeric.
# Orginal jpox does this in a switch statement. Since python does not
# have this statement, the dict method is chosen. To not duplicate this line
# over and over, the check is done seperately.
if token_type in (
TokenType.GREATER,
TokenType.GREATER_EQUAL,
TokenType.LESS,
TokenType.LESS_EQUAL,
TokenType.MINUS,
TokenType.SLASH,
TokenType.STAR,
):
self._check_number_operands(expr.operator, left, right)
choices = {
# Comparison operators
TokenType.GREATER:
lambda: float(left) > float(right),
TokenType.GREATER_EQUAL:
lambda: float(left) >= float(right),
TokenType.LESS:
lambda: float(left) < float(right),
TokenType.LESS_EQUAL:
lambda: float(left) <= float(right),
# Equality
TokenType.BANG_EQUAL:
lambda: not self._is_equal(left, right),
TokenType.EQUAL_EQUAL:
lambda: self._is_equal(left, right),
# Arithmetic operators
TokenType.MINUS:
lambda: float(left) - float(right),
TokenType.SLASH:
lambda: float(left) / float(right),
TokenType.STAR:
lambda: float(left) * float(right),
TokenType.PLUS:
lambda: self._binary_plus(expr, left, right),
}
try:
option = choices[token_type]
result = option()
return result
except KeyError:
raise YaploxRuntimeError(
expr.operator, f"Unknown operator {expr.operator.lexeme}")
def visit_call_expr(self, expr: Call):
function = self._evaluate(expr.callee)
arguments = [self._evaluate(argument) for argument in expr.arguments]
if not isinstance(function, YaploxCallable):
raise YaploxRuntimeError(expr.paren,
"Can only call functions and classes.")
# function = YaploxCallable(callee)
if len(arguments) != function.arity():
raise YaploxRuntimeError(
expr.paren,
f"Expected {function.arity()} arguments but got {len(arguments)}.",
)
return function.call(self, arguments)
def visit_get_expr(self, expr: Get):
obj = self._evaluate(expr.obj)
if isinstance(obj, YaploxInstance):
return obj.get(expr.name)
raise YaploxRuntimeError(expr.name, "Only instances have properties.")
def visit_grouping_expr(self, expr: Grouping):
return self._evaluate(expr.expression)
def visit_literal_expr(self, expr: Literal):
return expr.value
def visit_logical_expr(self, expr: Logical):
left = self._evaluate(expr.left)
if expr.operator.token_type == TokenType.OR:
if self._is_truthy(left):
return left
else:
if not self._is_truthy(left):
return left
return self._evaluate(expr.right)
def visit_set_expr(self, expr: Set):
obj = self._evaluate(expr.obj)
if not isinstance(obj, YaploxInstance):
raise YaploxRuntimeError(expr.name, "Only instances have fields.")
value = self._evaluate(expr.value)
obj.set(expr.name, value)
return value
def visit_super_expr(self, expr: Super):
distance = self.locals[expr]
superclass: YaploxClass = self.environment.get_at(distance=distance,
name="super")
obj = self.environment.get_at(distance=distance - 1, name="this")
method = superclass.find_method(expr.method.lexeme)
# Check that we have a super method
if method is None:
raise YaploxRuntimeError(
expr.method, f"Undefined property '{expr.method.lexeme}'.")
return method.bind(obj)
def visit_this_expr(self, expr: This):
return self._look_up_variable(expr.keyword, expr)
def visit_unary_expr(self, expr: Unary):
right = self._evaluate(expr.right)
token_type = expr.operator.token_type
if token_type == TokenType.MINUS:
self._check_number_operand(expr.operator, right)
return -float(right)
elif token_type == TokenType.BANG:
return not Interpreter._is_truthy(right)
@staticmethod
def _check_number_operand(operator: Token, operand: Any):
if isinstance(operand, (float, int)):
return
raise YaploxRuntimeError(operator, f"{operand} must be a number.")
@staticmethod
def _check_number_operands(operator: Token, left: Any, right: Any):
if isinstance(left, (float, int)) and isinstance(right, (float, int)):
return
raise YaploxRuntimeError(operator, "Operands must be numbers.")
@staticmethod
def _is_truthy(obj):
if obj is None:
return False
if isinstance(obj, bool):
return obj
return True
def _evaluate(self, expr: Expr):
return expr.accept(self)
def visit_variable_expr(self, expr: "Variable") -> Any:
return self._look_up_variable(expr.name, expr)
def _look_up_variable(self, name: Token, expr: Expr) -> Any:
distance = self.locals.get(expr)
if distance is not None:
return self.environment.get_at(distance, name.lexeme)
else:
return self.globals.get(name)
def visit_assign_expr(self, expr: "Assign") -> Any:
value = self._evaluate(expr.value)
distance = self.locals.get(expr)
if distance:
self.environment.assign_at(distance, expr.name, value)
else:
self.globals.assign(expr.name, value)
return value
# statement stuff
def visit_class_stmt(self, stmt: Class):
superclass = None
if stmt.superclass is not None:
superclass = self._evaluate(stmt.superclass)
if not isinstance(superclass, YaploxClass):
raise YaploxRuntimeError(stmt.superclass.name,
"Superclass must be a class.")
self.environment.define(stmt.name.lexeme, None)
if stmt.superclass is not None:
self.environment = Environment(self.environment)
self.environment.define("super", superclass)
methods: Dict[str, YaploxFunction] = {}
for method in stmt.methods:
function = YaploxFunction(method, self.environment,
method.name.lexeme == "init")
methods[method.name.lexeme] = function
klass = YaploxClass(name=stmt.name.lexeme,
superclass=superclass,
methods=methods)
if stmt.superclass is not None:
self.environment = self.environment.enclosing # type: ignore
self.environment.assign(stmt.name, klass)
def visit_expression_stmt(self, stmt: Expression) -> None:
return self._evaluate(stmt.expression)
def visit_function_stmt(self, stmt: Function) -> None:
function = YaploxFunction(stmt, self.environment, False)
self.environment.define(stmt.name.lexeme, function)
def visit_if_stmt(self, stmt: If) -> None:
if self._is_truthy(self._evaluate(stmt.condition)):
self._execute(stmt.then_branch)
elif stmt.else_branch is not None:
self._execute(stmt.else_branch)
def visit_while_stmt(self, stmt: While) -> None:
while self._is_truthy(self._evaluate(stmt.condition)):
self._execute(stmt.body)
def visit_print_stmt(self, stmt: Print) -> None:
value = self._evaluate(stmt.expression)
print(self._stringify(value))
def visit_return_stmt(self, stmt: Return) -> None:
value = None
if stmt.value:
value = self._evaluate(stmt.value)
raise YaploxReturnException(value=value)
def visit_var_stmt(self, stmt: "Var") -> None:
value = None
if stmt.initializer is not None:
value = self._evaluate(stmt.initializer)
self.environment.define(stmt.name.lexeme, value)
def visit_block_stmt(self, stmt: "Block") -> None:
self.execute_block(stmt.statements, Environment(self.environment))
def execute_block(self, statements: List[Stmt], environment: Environment):
previous_env = self.environment
try:
self.environment = environment
for statement in statements:
self._execute(statement)
finally:
self.environment = previous_env
def visit_block_stmt(self, stmt: "Block") -> None:
self.execute_block(stmt.statements, Environment(self.environment))
def test_environment(self, create_token_factory):
env = Environment()
foo_token = create_token_factory(token_type=TokenType.VAR,
lexeme="Foo")
bar_token = create_token_factory(token_type=TokenType.VAR,
lexeme="Bar")
env.define("Foo", "Bar")
assert env.get(foo_token) == "Bar"
# This token isn't present
with pytest.raises(YaploxRuntimeError):
env.get(bar_token)
# Test assign
# Assign a new value to an existing key
env.assign(foo_token, "New_value")
assert env.get(foo_token) == "New_value"
# Assigning to a new value is not possible
with pytest.raises(YaploxRuntimeError):
env.assign(bar_token, "Foo")
def test_environment_distance(self, create_token_factory):
# Setup a few linked Environments
global_env = Environment()
local_1 = Environment(enclosing=global_env)
local_2 = Environment(enclosing=local_1)
local_3 = Environment(enclosing=local_2)
# Set some variables:
# Set a value to the global, that is available in local
create_token_factory(token_type=TokenType.VAR, lexeme="global_token")
global_env.define("global_token", "global_token")
# Set a variable on the 1st level:
create_token_factory(token_type=TokenType.VAR, lexeme="level_1")
local_1.define("level_1", "level_1")
# Get at a distance:
assert local_3.get_at(2, "level_1") == "level_1"
# It shouldn't be able to find this, level too shallow
assert local_3.get_at(1, "level_1") is None
# And try to find a global var
assert local_3.get_at(3, "global_token") == "global_token"
def test_environment_enclosure(self, create_token_factory):
global_env = Environment()
local_env = Environment(enclosing=global_env)
# Set a value to the global, that is available in local
foo_token = create_token_factory(token_type=TokenType.VAR,
lexeme="Foo")
global_env.define("Foo", "42")
# And retrieve it in the local env:
assert local_env.get(foo_token) == "42"
# Assign it a new value in the local env should also work:
local_env.assign(foo_token, "New value")
# And retrieve it in the local env:
assert global_env.get(foo_token) == "New value"
assert local_env.get(foo_token) == "New value"
# Override the value in the local env:
local_env.define("Foo", "Local variable")
# This must override the local env, but keep global env the same.
assert global_env.get(foo_token) == "New value"
assert local_env.get(foo_token) == "Local variable"