class Interpreter:
def __init__(self):
self.lines = {}
self._program_counter = 0
self._running = False
self._stack = []
self._variables = {}
self._parser = Parser(self._variables)
def interactive(self):
while True:
line = input('>')
if len(line):
self.interpret_line(line)
def interpret_line(self, line):
tokenizer = Tokenizer()
tokenizer.parse(line)
first_token = tokenizer.getNextToken()
if first_token.type == Token.NUMBER:
self.lines[int(first_token.value)] = tokenizer.prog[tokenizer.pos:]
self.sort_lines()
else:
self.run_line(line)
def run_line(self, line):
tokenizer = Tokenizer()
tokenizer.parse(line)
self.execute_statement(tokenizer)
def execute_statement(self, tokenizer):
statement = self._parser.match_statement(tokenizer)
if statement == 'LET':
self.stat_let(tokenizer)
elif statement == 'PRINT':
self.stat_print(tokenizer)
elif statement == 'LIST':
self.stat_list()
elif statement == 'INPUT':
self.stat_input(tokenizer)
elif statement == 'IF':
self.stat_if(tokenizer)
elif statement == 'RUN':
self.run_program()
elif statement == 'END':
self.stat_end()
elif statement == 'GOTO':
self.stat_goto(tokenizer)
elif statement == 'GOSUB':
self.stat_gosub(tokenizer)
elif statement == 'RETURN':
self.stat_return()
else:
raise Exception('Unrecognised statement: ' + statement.value)
def run_program(self):
self._program_counter = 0
self._running = True
self.sort_lines()
statements = [x for x in self.lines.values()]
while self._program_counter < len(statements) and self._running:
statement = statements[self._program_counter]
self.run_line(statement)
self._program_counter += 1
def sort_lines(self):
self.lines = OrderedDict(sorted(self.lines.items(), key=lambda x: x[0]))
def stat_let(self, tokenizer):
variable = tokenizer.getNextToken()
if variable.type != Token.VARIABLE:
raise Exception("Expected a variable")
if tokenizer.getNextToken().type != Token.EQUALS:
raise Exception('Expected an equals')
self._parser._variables[variable.value] = self._parser.match_expression(tokenizer)
def stat_print(self, tokenizer):
list = self._parser.match_expression_list(tokenizer)
print(','.join([str(i) for i in list]))
def stat_list(self):
for no, line in iter(self.lines.items()):
print(no, line,)
def stat_input(self, tokenizer):
vars = self._parser.match_var_list(tokenizer)
for var in vars:
self._parser._variables[var] = input("?")
def stat_if(self, tokenizer):
result = self._parser.match_relop(tokenizer)
then = tokenizer.getNextToken()
if then.type != Token.COMMAND or then.value != 'THEN':
raise Exception('Expected then after relative operator')
if result:
self.execute_statement(tokenizer)
def stat_end(self):
self._running = False
def stat_goto(self, tokenizer):
line_number = self._parser.match_expression(tokenizer)
self.sort_lines()
line_numbers = [x for x in self.lines.keys()]
self._program_counter = line_numbers.index(line_number) - 1
def stat_gosub(self, tokenizer):
self._stack.append(self._program_counter)
self.stat_goto(tokenizer)
def stat_return(self):
self._program_counter = self._stack.pop()
class TestParser(TestCase):
def setUp(self):
self.tokenizer = Tokenizer()
self.parser = Parser({})
def test_match_var_list(self):
self.tokenizer.parse('A, B, C')
self.assertEqual(['A', 'B', 'C'], self.parser.match_var_list(self.tokenizer))
def test_match_relop(self):
self.tokenizer.parse('2 > 1')
self.assertEqual(1, self.parser.match_relop(self.tokenizer))
self.tokenizer.parse('2 < 1')
self.assertEqual(0, self.parser.match_relop(self.tokenizer))
self.tokenizer.parse('2 <= 2')
self.assertEqual(1, self.parser.match_relop(self.tokenizer))
self.tokenizer.parse('2 <= 1')
self.assertEqual(0, self.parser.match_relop(self.tokenizer))
self.tokenizer.parse('2 >= 2')
self.assertEqual(1, self.parser.match_relop(self.tokenizer))
self.tokenizer.parse('2 >= 3')
self.assertEqual(0, self.parser.match_relop(self.tokenizer))
self.tokenizer.parse('2 = 2')
self.assertEqual(1, self.parser.match_relop(self.tokenizer))
self.tokenizer.parse('2 = 3')
self.assertEqual(0, self.parser.match_relop(self.tokenizer))
self.tokenizer.parse('2 <> 3')
self.assertEqual(1, self.parser.match_relop(self.tokenizer))
self.tokenizer.parse('2 <> 2')
self.assertEqual(0, self.parser.match_relop(self.tokenizer))
self.tokenizer.parse('2 >< 3')
self.assertEqual(1, self.parser.match_relop(self.tokenizer))
self.tokenizer.parse('2 >< 2')
self.assertEqual(0, self.parser.match_relop(self.tokenizer))
def test_match_expression_list(self):
self.tokenizer.parse('2+3+2*2, 1+2, 3, "abcd"')
self.assertEqual([9,3,3, 'abcd'], self.parser.match_expression_list(self.tokenizer))
def test_match_expression(self):
self.tokenizer.parse('2+3+2*2')
self.assertEqual(9, self.parser.match_expression(self.tokenizer))
def test_match_term(self):
self.tokenizer.parse('2*3*4')
self.assertEqual(24, self.parser.match_term(self.tokenizer))
def test_match_factor(self):
self.tokenizer.parse('123')
self.assertEqual(123, self.parser.match_factor(self.tokenizer))
self.parser._variables['A'] = 456
self.tokenizer.parse('A')
self.assertEqual(456, self.parser.match_factor(self.tokenizer))
def test_match_brackets(self):
self.tokenizer.parse('(1 + 2) * (3 + 5)')
self.assertEqual(24, self.parser.match_expression(self.tokenizer))
def test_left_associativity(self):
self.tokenizer.parse('10-2+2')
self.assertEqual(10, self.parser.match_term(self.tokenizer))