def test_div(self):
env = Env(expr.Const, expr.NO_VALUE)
three = expr.Const(3)
nine = expr.Const(9)
x = expr.Var('x')
y = expr.Var('y')
self.assertEqual(expr.Div(x, y), expr.Div(x, y))
self.assertNotEqual(expr.Div(x, y), expr.Times(x, y))
self.assertEqual(expr.Div(nine, three).eval(env), expr.Const(3))
self.assertEqual(
expr.Div(nine, expr.Times(three, three)).eval(env), expr.Const(1))
def test_times(self):
env = Env(expr.Const, expr.NO_VALUE)
three = expr.Const(3)
four = expr.Const(4)
x = expr.Var('x')
y = expr.Var('y')
self.assertEqual(expr.Times(x, y), expr.Times(x, y))
self.assertNotEqual(expr.Times(x, y), expr.Plus(x, y))
self.assertEqual(expr.Times(three, four).eval(env), expr.Const(12))
self.assertEqual(
expr.Times(three, expr.Times(three, four)).eval(env),
expr.Const(36))
def test_plus(self):
env = Env(expr.Const, expr.NO_VALUE)
eight = expr.Const(8)
nine = expr.Const(9)
x = expr.Var('x')
y = expr.Var('y')
self.assertEqual(expr.Plus(x, y), expr.Plus(x, y))
self.assertEqual(expr.Plus(eight, nine).eval(env), expr.Const(17))
self.assertEqual(
expr.Plus(eight, expr.Plus(nine, eight)).eval(env), expr.Const(25))
self.assertEqual(repr(expr.Plus(eight, nine)),
"Plus(Const(8),Const(9))")
self.assertEqual(str(expr.Plus(eight, nine)), "(8 + 9)")
def test_assign(self):
"""Assignments: Assign(var, exp) """
env = Env(expr.Const, expr.ZERO)
x = expr.Var('x')
y = expr.Var('y')
# y is undefined here, should give value 0,
# giving x value 9
assignment = expr.Assign(x, expr.Plus(y, expr.Const(9)))
# print(assignment)
x_exp = assignment.eval(env)
y_val = expr.Assign(y, expr.Const(3)).eval(env)
# y == 3, x == 9 here
result = expr.Plus(x, expr.Const(4)).eval(env)
self.assertEqual(result, expr.Const(13))
def _primary(stream: TokenStream) -> expr.Expr:
"""Constants, Variables, and parenthesized expressions"""
log.debug(f"Parsing primary with starting token {stream.peek()}")
token = stream.take()
if token.kind is TokenCat.CONST:
log.debug(f"Returning Const node from token {token}")
return expr.Const(int(token.value))
elif token.kind is TokenCat.IDENT:
log.debug(f"Variable {token.value}")
return expr.Var(token.value)
elif token.kind is TokenCat.LPAREN:
nested = _expr(stream)
require(stream, TokenCat.RPAREN, consume=True)
return nested
else:
raise InputError(f"Confused about {token} in expression")
def _stmt(stream: TokenStream) -> expr.Expr:
"""
assignment ::= IDENT '=' expression ';'
"""
if stream.peek().kind is TokenCat.WHILE:
return _while(stream)
if stream.peek().kind is TokenCat.IF:
return _if(stream)
if stream.peek().kind is not TokenCat.IDENT:
raise InputError(f"Expecting identifier at beginning of assignment, got {stream.peek()}")
target = expr.Var(stream.take().value)
if stream.peek().kind is not TokenCat.ASSIGN:
raise InputError("Expecting assignment symbol, got {stream.peek()}")
stream.take() # Discard token
value = _expr(stream)
if stream.peek().kind is not TokenCat.SEMI:
raise InputError(f"Expecting semicolon after assignment, got {stream.peek()}")
stream.take() # Discard token
return expr.Assign(target, value)