class Interpreter(Visitor):
"""
Interpreter inherit from Visitor and interpret it when visiting the abstract syntax tree
"""
def __init__(self, parser: Parser):
self.parser = parser
self.analyzer = SemanticAnalyzer()
self.callstack = CallStack()
def error(self, error_code: ErrorCode, token):
raise RuntimeError(
error_code=error_code,
token=token,
message=f'{error_code.value} -> {token}',
)
def log(self, msg):
print(msg)
def visit_binop(self, node: BinOp):
left_val = self.visit(node.left)
right_val = self.visit(node.right)
# todo type checker
if node.op.type is TokenType.PLUS:
return left_val + right_val
elif node.op.type is TokenType.MINUS:
return left_val - right_val
elif node.op.type is TokenType.MUL:
return left_val * right_val
elif node.op.type is TokenType.INTEGER_DIV:
return left_val // right_val
elif node.op.type is TokenType.FLOAT_DIV:
return left_val / right_val
elif node.op.type is TokenType.MOD:
return left_val % right_val
elif node.op.type is TokenType.AND:
return left_val and right_val
elif node.op.type is TokenType.OR:
return left_val or right_val
elif node.op.type is TokenType.EQUALS:
return left_val == right_val
elif node.op.type is TokenType.NOT_EQUALS:
return left_val != right_val
elif node.op.type is TokenType.GREATER:
return left_val > right_val
elif node.op.type is TokenType.GREATER_EQUALS:
return left_val >= right_val
elif node.op.type is TokenType.LESS:
return left_val < right_val
elif node.op.type is TokenType.LESS_EQUALS:
return left_val <= right_val
def visit_num(self, node: Num):
return node.value
def visit_boolean(self, node: Boolean):
return node.value
def visit_unaryop(self, node: UnaryOp):
if node.op.type is TokenType.PLUS:
return +self.visit(node.factor)
if node.op.type is TokenType.MINUS:
return -self.visit(node.factor)
if node.op.type is TokenType.NOT:
return not self.visit(node.factor)
def visit_compound(self, node: Compound):
for child in node.childrens:
self.visit(child)
def visit_var(self, node: Var):
current_frame: Frame = self.callstack.peek()
# get value by variable's name
val = current_frame.get_value(node.name)
return val
def visit_assign(self, node: Assign):
var_name = node.left.name # get variable's name
var_value = self.visit(node.right)
current_frame: Frame = self.callstack.peek()
if current_frame.type is FrameType.FUNCTION and current_frame.name == var_name:
current_frame.return_val = var_value
else:
current_frame.set_value(var_name, var_value)
def visit_program(self, node: Program):
program_name = node.name
self.log(f'ENTER: PROGRAM {program_name}')
frame = Frame(name=program_name, type=FrameType.PROGRAM)
self.callstack.push(frame)
self.visit(node.block)
self.log(str(self.callstack))
self.callstack.pop()
self.log(f'LEAVE: PROGRAM {program_name}')
def visit_block(self, node: Block):
for declaration in node.declarations:
self.visit(declaration)
self.visit(node.compound_statement)
def visit_vardecl(self, node: VarDecl):
var_name = node.var_node.name
current_frame: Frame = self.callstack.peek()
current_frame.define(var_name)
def visit_procdecl(self, node: ProcedureDecl):
proc_name = node.token.value
current_frame: Frame = self.callstack.peek()
current_frame.define(proc_name)
current_frame.set_value(proc_name, node)
def visit_proccall(self, node: ProcedureCall):
proc_name = node.proc_name
current_frame = self.callstack.peek()
proc_node: ProcedureDecl = current_frame.get_value(proc_name)
self.log(f'ENTER: PROCEDURE {proc_name}')
# get actual params values
actual_param_values = [
self.visit(actual_param) for actual_param in node.actual_params
]
proc_frame = Frame(name=proc_name, type=FrameType.PROCEDURE)
self.callstack.push(proc_frame)
current_frame: Frame = self.callstack.peek()
# map actual params to formal params
for (formal_param, actual_param_value) in zip(proc_node.params,
actual_param_values):
current_frame.define(formal_param.var_node.name)
current_frame.set_value(formal_param.var_node.name,
actual_param_value)
self.visit(proc_node.block)
self.log(str(self.callstack))
self.callstack.pop()
self.log(f'LEAVE: PROCEDURE {proc_name}')
def visit_funcdecl(self, node: FunctionDecl):
func_name = node.token.value
current_frame: Frame = self.callstack.peek()
current_frame.define(func_name)
current_frame.set_value(func_name, node)
def visit_funccall(self, node: FunctionCall):
current_frame = self.callstack.peek()
func_name = node.func_name
func_node: FunctionDecl = current_frame.get_value(func_name)
self.log(f'ENTER: FUNCTION {func_name}')
func_frame = Frame(name=func_name, type=FrameType.FUNCTION)
self.callstack.push(func_frame)
current_frame: Frame = self.callstack.peek()
# get actual params values to formal params
actual_param_values = [
self.visit(actual_param) for actual_param in node.actual_params
]
for (formal_param, actual_param_value) in zip(func_node.params,
actual_param_values):
current_frame.define(formal_param.var_node.name)
current_frame.set_value(formal_param.var_node.name,
actual_param_value)
self.visit(func_node.block)
self.log(str(self.callstack))
self.log(f'LEAVE: FUNCTION {func_name}')
return_val = current_frame.return_val
self.callstack.pop()
if return_val is None:
self.error(error_code=ErrorCode.MISSING_RETURN, token=node.token)
return return_val
def visit_condition(self, node: Condition):
if self.visit(node.condition_node):
self.visit(node.then_node)
elif node.else_node is not None:
self.visit(node.else_node)
def visit_then(self, node: Then):
self.visit(node.child)
def visit_else(self, node: Else):
self.visit(node.child)
def visit_while(self, node: WhileLoop):
while self.visit(node.conditon_node) is True:
try:
self.visit(node.body_node)
except ContinueError:
continue
except BreakError:
break
def visit_continue(self, node: Continue):
raise ContinueError()
def visit_break(self, node: Break):
raise BreakError()
def interpret(self):
ast = self.parser.parse()
self.analyzer.visit(ast)
self.visit(ast)