def test__cps_if(self):
if_ast = IfAst(LiteralAst(1), LiteralAst(2), LiteralAst(3))
cps_ast = _cps_if(if_ast, lambda x: x)
expected_ast = CallAst(
LambdaAst(
'', cps_ast.func.params,
IfAst(LiteralAst(1),
CallAst(VarAst(cps_ast.func.params[0]), [LiteralAst(2)]),
CallAst(VarAst(cps_ast.func.params[0]),
[LiteralAst(3)]))), [
LambdaAst('', cps_ast.args[0].params,
VarAst(cps_ast.args[0].params[0]))
])
self.assertEqual(cps_ast, expected_ast)
if_ast = IfAst(
LiteralAst(1),
LiteralAst(2),
LiteralAst(False),
)
cps_ast = _cps_if(if_ast, lambda x: x)
expected_ast = CallAst(
LambdaAst(
'', cps_ast.func.params,
IfAst(
LiteralAst(1),
CallAst(VarAst(cps_ast.func.params[0]), [LiteralAst(2)]),
CallAst(VarAst(cps_ast.func.params[0]),
[LiteralAst(False)]))), [
LambdaAst('', cps_ast.args[0].params,
VarAst(cps_ast.args[0].params[0]))
])
self.assertEqual(cps_ast, expected_ast)
def test_to_cps(self):
js_raw_ast = JsAst("aa")
cps_ast = _cps_js_raw(js_raw_ast, lambda x: x)
self.assertEqual(cps_ast, js_raw_ast)
atom_ast = LiteralAst(1.0)
cps_ast = to_cps(atom_ast, lambda x: x)
self.assertEqual(atom_ast, cps_ast)
let_ast = LetAst([], LiteralAst(False))
cps_ast = to_cps(let_ast, lambda x: x)
self.assertEqual(cps_ast, LiteralAst(False))
prog_ast = ProgAst([])
cps_ast = to_cps(prog_ast, lambda x: x)
self.assertEqual(cps_ast, LiteralAst(False))
prog_ast = ProgAst([LiteralAst(1)])
cps_ast = to_cps(prog_ast, lambda x: x)
self.assertEqual(cps_ast, LiteralAst(1))
prog_ast = ProgAst([LiteralAst(1), LiteralAst(2)])
cps_ast = to_cps(prog_ast, lambda x: x)
self.assertEqual(cps_ast, ProgAst([LiteralAst(1), LiteralAst(2)]))
if_ast = IfAst(LiteralAst(1), LiteralAst(2), LiteralAst(3))
cps_ast: CallAst = to_cps(if_ast, lambda x: x)
expected_ast = CallAst(
LambdaAst(
'', cps_ast.func.params,
IfAst(LiteralAst(1),
CallAst(VarAst(cps_ast.func.params[0]), [LiteralAst(2)]),
CallAst(VarAst(cps_ast.func.params[0]),
[LiteralAst(3)]))), [
LambdaAst('', cps_ast.args[0].params,
VarAst(cps_ast.args[0].params[0]))
])
self.assertEqual(cps_ast, expected_ast)
lambda_ast = LambdaAst('', ['x', 'y'], LiteralAst(1))
cps_ast = to_cps(lambda_ast, lambda x: x)
expected_ast = LambdaAst(
'', [cps_ast.params[0]] + ['x', 'y'],
CallAst(VarAst(cps_ast.params[0]), [LiteralAst(1)]))
self.assertEqual(cps_ast, expected_ast)
binary_ast = BinaryAst('+', LiteralAst(1), LiteralAst(2))
cps_ast = to_cps(binary_ast, lambda x: x)
self.assertEqual(cps_ast, binary_ast)
parse = Parser(TokenStream(InputStream("a = foo(10);")))
cps_ast = to_cps(parse(), lambda x: x)
expected_ast = CallAst(VarAst('foo'), [
LambdaAst(
'', [cps_ast.args[0].params[0]],
AssignAst(VarAst('a'), VarAst(cps_ast.args[0].params[0]))),
LiteralAst(10)
])
self.assertEqual(cps_ast, expected_ast)
def _cps_lambda(lambda_ast: LambdaAst, k: Callable[[Ast], Ast]) -> Ast:
continuation = gensym("K")
body = to_cps(
lambda_ast.body,
lambda lambda_body: CallAst(VarAst(continuation), [lambda_body]))
return k(
LambdaAst(lambda_ast.name, [continuation] + lambda_ast.params, body))
def _cps_if(if_ast: IfAst, k: Callable[[Ast], Ast]) -> CallAst:
"""
The previous version of cps_if passed the k on compiling both branches,
resulting in massive code growth for consecutive if-s.
The (quite expensive) fix is to wrap the rest of the program
in a continuation, and we'll transform the "if" node into an IIFE
which receives that continuation as an argument.
The body of this IIFE will just call the continuation
with the result of the if expression.
The following is a sample transformation:
a = if foo then 1 else 2;
print(a);
(λ (ifcont){
if foo then ifcont(1) else ifcont(2);
})(λ (ifret){
a = ifret;
print(a);
});
"""
def cps_cond(cond_ast: Ast) -> Ast:
def cps_then_and_else(result: Ast) -> Ast:
return CallAst(VarAst(if_continuation), [result])
return IfAst(cond_ast, to_cps(if_ast.then, cps_then_and_else),
to_cps(if_ast.else_, cps_then_and_else))
if_continuation = gensym("I")
return CallAst(
LambdaAst('', [if_continuation], to_cps(if_ast.cond, cps_cond)),
[_make_continuation(k)])
def _parse_lambda(self, keyword: str) -> LambdaAst:
self._skip_kw(keyword)
if self._token_stream.peek().type == 'var':
name = self._token_stream.next().value
else:
name = ''
params = self._delimited("(", ")", ",", self._parse_varname)
body = self._parse_expression()
return LambdaAst(name, params, body)
def test__cps_lambda(self):
# lambda (x, y) 1
lambda_ast = LambdaAst('', ['x', 'y'], LiteralAst(1))
cps_ast = _cps_lambda(lambda_ast, lambda x: x)
expected_ast = LambdaAst(
'', [cps_ast.params[0]] + ['x', 'y'],
CallAst(VarAst(cps_ast.params[0]), [LiteralAst(1)]))
self.assertEqual(cps_ast, expected_ast)
# lambda (x, y) x + y
lambda_ast = LambdaAst('', ['x', 'y'],
BinaryAst('+', VarAst('x'), VarAst('y')))
cps_ast = _cps_lambda(lambda_ast, lambda x: x)
# expected result: lambda (continue, args) continue(body)
expected_ast = LambdaAst(
'', [cps_ast.params[0]] + ['x', 'y'],
CallAst(VarAst(cps_ast.params[0]),
[BinaryAst('+', VarAst('x'), VarAst('y'))]))
self.assertEqual(cps_ast, expected_ast)
def _js_let(ast: LetAst) -> str:
if not ast.vardefs:
return _to_js(ast.body)
# immediately invoked function expression
iife = CallAst(
LambdaAst('', [ast.vardefs[0].name], LetAst(ast.vardefs[1:],
ast.body)),
[ast.vardefs[0].define or LiteralAst(False)])
return f'({_to_js(iife)})'
def _optimize_lambda_ast(self, ast: LambdaAst) -> Ast:
# lambda x(args) y(args) can be optimized to y,
# a kind of tail call optimization
if isinstance(ast.body, CallAst):
# same args
if len(ast.params) == len(ast.body.args) \
and all(isinstance(arg, VarAst) and arg.name == param for arg, param in
zip(ast.body.args, ast.params)):
func = ast.body.func
# If y is one of x's params, then the value of y is not decided
# until x is called.
if isinstance(func, VarAst) and (func.name not in ast.params):
# y is parameter of enclosing lambda function of x.
# In original version, the value of y is queried from environment
# when x is called. In optimized version, lambda x(args) y(args)
# is replaced with y, the value of y is queried when optimize occurs.
# So the value of y remains unchanged.
# Look at following example:
# y = some lambda
# foo = lambda x(args) y(args)
# y = another lambda
# foo(args)
#
# the result is (another lambda)(args)
#
# the optimized version:
# y = some lambda
# foo = y
# y = another lambda
# foo(args)
#
# the result is (some lambda)(args)
if func.define.assigned == 0:
self.changes += 1
return self._optimize_aux(ast.body.func)
ast.iife_params = [
param for param in ast.iife_params if ast.env.get(param).refs
]
save = self.closure
self.closure = ast
ast.body = self._optimize_aux(ast.body)
self.closure = save
return ast
def _cps_let(let_ast: LetAst, k: Callable[[Ast], Ast]) -> Ast:
if not let_ast.vardefs:
return to_cps(let_ast.body, k)
return to_cps(
CallAst(
LambdaAst('', [let_ast.vardefs[0].name],
LetAst(let_ast.vardefs[1:], let_ast.body)), [
let_ast.vardefs[0].define
if let_ast.vardefs[0].define else LiteralAst(False)
]), k)
def test__cps_let(self):
# let_ast = LetAst(
# [VarDefAst('a', LiteralAst(1)), VarDefAst('b', LiteralAst("a"))],
# LiteralAst(False))
let_ast = LetAst(
[],
LiteralAst(False),
)
cps_ast = _cps_let(let_ast, lambda x: x)
self.assertEqual(cps_ast, LiteralAst(False))
let_ast = LetAst([VarDefAst('a', LiteralAst(1))], VarAst('a'))
cps_ast = _cps_let(let_ast, lambda x: x)
self.assertEqual(
cps_ast,
CallAst(
LambdaAst(
'', [cps_ast.func.params[0], 'a'],
CallAst(VarAst(cps_ast.func.params[0]), [VarAst('a')])), [
LambdaAst('', [cps_ast.args[0].params[0]],
VarAst(cps_ast.args[0].params[0])),
LiteralAst(1)
]))
def test__cps_call(self):
call_ast = CallAst(VarAst('foo'), [LiteralAst(1), LiteralAst(2)])
cps_ast = _cps_call(call_ast, lambda x: x)
expected_ast = CallAst(VarAst('foo'), [
LambdaAst(
'',
[cps_ast.args[0].params[0]],
VarAst(cps_ast.args[0].params[0]),
),
LiteralAst(1),
LiteralAst(2)
])
self.assertEqual(cps_ast, expected_ast)
def parser() -> Ast:
ast = self._maybe_binary(self._parse_atom(), 0)
# relational operator short-circuit implementation
if isinstance(ast, BinaryAst):
# left || right -> (lambda (left) {
# if left then left else right})(left)
binary_ast = cast(BinaryAst, ast)
if binary_ast.operator == '||':
iife_param = gensym('left')
ast = CallAst(
LambdaAst(
'',
[iife_param],
IfAst(
VarAst(iife_param),
VarAst(iife_param),
binary_ast.right)),
[binary_ast.left])
elif binary_ast.operator == '&&':
ast = IfAst(binary_ast.left, binary_ast.right, LiteralAst(False))
return ast
def _parse_let(self) -> Union[CallAst, LetAst]:
"""
When it is a named let, if an arg is not followed by some expression,
then a false value is assigned to the arg by the parser.
:return:
"""
self._skip_kw('let')
if self._token_stream.peek().type == 'var':
name = self._token_stream.next().value
vardefs = self._delimited('(', ')', ',', self._parse_vardef)
varnames = [vardef.name for vardef in vardefs]
defines = [vardef.define if vardef.define else LiteralAst(False)
for vardef in vardefs]
return CallAst(
LambdaAst(
name,
varnames,
self._parse_expression()),
defines)
vardefs = self._delimited('(', ')', ',', self._parse_vardef)
body = self._parse_expression()
return LetAst(vardefs, body)
def test_evaluate(self):
ast = LiteralAst(1.0)
environment = Environment()
evaluate(ast, environment, lambda value: self.assertEqual(value, 1.0))
ast = LiteralAst(True)
environment = Environment()
evaluate(ast, environment, self.assertTrue)
ast = LiteralAst(False)
environment = Environment()
evaluate(ast, environment, self.assertFalse)
ast = LiteralAst("aaa")
evaluate(ast, Environment(),
lambda value: self.assertEqual(value, "aaa"))
ast = BinaryAst('+', LiteralAst(1), LiteralAst(2))
evaluate(ast, Environment(),
lambda value: self.assertEqual(value, 3.0))
ast = ProgAst([])
evaluate(ast, Environment(), self.assertFalse)
ast = ProgAst([LiteralAst(1)])
evaluate(ast, Environment(),
lambda value: self.assertEqual(value, 1.0))
ast = ProgAst([LiteralAst(1), LiteralAst(2)])
evaluate(ast, Environment(),
lambda value: self.assertEqual(value, 2.0))
ast = AssignAst(LiteralAst(1), LiteralAst("a"))
with self.assertRaises(Exception):
evaluate(ast, Environment(), lambda value: value)
ast = ProgAst([AssignAst(VarAst('a'), LiteralAst("foo")), VarAst('a')])
evaluate(ast, Environment(),
lambda value: self.assertEqual(value, "foo"))
ast = AssignAst(VarAst("a"), LiteralAst("foo"))
with self.assertRaises(Exception):
evaluate(ast, Environment(Environment()), lambda value: value)
ast = CallAst(
LambdaAst("", ["a"], VarAst("a")),
[LiteralAst(1)],
)
evaluate(ast, Environment(),
lambda value: self.assertEqual(value, 1.0))
ast = CallAst(LambdaAst("", ["a"], VarAst("a")), [LiteralAst("abc")])
evaluate(ast, Environment(),
lambda value: self.assertEqual(value, "abc"))
# # (λ loop (n) if n > 0 then n + loop(n - 1) else 0) (10)
ast = CallAst(
LambdaAst(
"loop", ["n"],
IfAst(
BinaryAst(">", VarAst("n"), LiteralAst(0)),
BinaryAst(
"+", VarAst("n"),
CallAst(VarAst("loop"),
[BinaryAst('-', VarAst('n'), LiteralAst(1))])),
LiteralAst(0))), [LiteralAst(10)])
evaluate(ast, Environment(),
lambda value: self.assertEqual(value, 55.0))
# # let (x) x;
ast = LetAst([VarDefAst("x", None)], VarAst("x"))
evaluate(ast, Environment(), self.assertFalse)
# # let (x = 2, y = x + 1, z = x + y) x + y + z
ast = LetAst([
VarDefAst("x", LiteralAst(2)),
VarDefAst("y", BinaryAst("+", VarAst("x"), LiteralAst(1))),
VarDefAst("z", BinaryAst("+", VarAst("x"), VarAst("y")))
], BinaryAst("+", BinaryAst("+", VarAst("x"), VarAst("y")),
VarAst("z")))
evaluate(ast, Environment(),
lambda value: self.assertEqual(value, 10.0))
# # the second expression will result an errors,
# since x, y, z are bound to the let body
# # let (x = 2, y = x + 1, z = x + y) x + y + z; x + y + z
ast = ProgAst([
LetAst([
VarDefAst('x', LiteralAst(2)),
VarDefAst('y', BinaryAst('+', VarAst('x'), LiteralAst(1))),
VarDefAst('z', BinaryAst('+', VarAst('x'), VarAst('y')))
],
BinaryAst('+', BinaryAst('+', VarAst('x'), VarAst('y')),
VarAst('z'))),
BinaryAst('+', BinaryAst('+', VarAst('x'), VarAst('y')),
VarAst('z'))
])
with self.assertRaises(Exception):
evaluate(ast, Environment(), lambda value: value)
ast = IfAst(LiteralAst(""), LiteralAst(1), None)
evaluate(ast, Environment(),
lambda value: self.assertEqual(value, 1.0))
ast = IfAst(LiteralAst(False), LiteralAst(1), LiteralAst(2))
evaluate(ast, Environment(),
lambda value: self.assertEqual(value, 2.0))
ast = IfAst(LiteralAst(False), LiteralAst(1), LiteralAst(False))
evaluate(ast, Environment(), self.assertFalse)
ast = {"type": "foo", "value": 'foo'}
with self.assertRaises(Exception):
evaluate(ast, Environment(), lambda value: value)
# fib = λ(n) if n < 2 then n else fib(n - 1) + fib(n - 2);
# fib(6);
#
ast = ProgAst([
AssignAst(
VarAst('fib'),
LambdaAst(
'n', ['n'],
IfAst(
BinaryAst('<', VarAst('n'), LiteralAst(2)),
VarAst('n'),
BinaryAst(
'+',
CallAst(
VarAst('fib'),
[BinaryAst('-', VarAst('n'), LiteralAst(1))]),
CallAst(
VarAst('fib'),
[BinaryAst('-', VarAst('n'), LiteralAst(2))
]))))),
CallAst(VarAst('fib'), [LiteralAst(6)])
])
evaluate(ast, Environment(),
lambda value: self.assertEqual(value, 8.0))
ast = IfAst(LiteralAst(False), LiteralAst(1), LiteralAst(False))
evaluate(ast, Environment(), self.assertFalse)
ast = CallAst(LiteralAst(1), [])
with self.assertRaises(Exception):
evaluate(ast, Environment(), self.assertFalse)
code = """
2 + twice(3, 4)
"""
global_env = Environment()
for name, func in primitive.items():
global_env.define(name, func)
parser = Parser(TokenStream(InputStream(code)))
evaluate(parser(), global_env, lambda result: result)
def test_evaluate(self):
ast = LiteralAst(1.0)
environment = Environment()
self.assertEqual(evaluate(ast, environment), 1.0)
ast = LiteralAst(True)
environment = Environment()
self.assertEqual(evaluate(ast, environment), True)
ast = LiteralAst(False)
environment = Environment()
self.assertEqual(evaluate(ast, environment), False)
ast = LiteralAst("aaa")
self.assertEqual(evaluate(ast, Environment()), "aaa")
ast = BinaryAst('+', LiteralAst(1), LiteralAst(2))
self.assertEqual(evaluate(ast, Environment()), 3.0)
ast = ProgAst([])
self.assertEqual(evaluate(ast, Environment()), False)
ast = ProgAst([LiteralAst(1)])
self.assertEqual(evaluate(ast, Environment()), 1.0)
ast = ProgAst([LiteralAst(1), LiteralAst(2)])
self.assertEqual(evaluate(ast, Environment()), 2.0)
ast = AssignAst(LiteralAst(1), LiteralAst("a"))
with self.assertRaises(Exception):
evaluate(ast, Environment())
ast = ProgAst([AssignAst(VarAst('a'), LiteralAst("foo")), VarAst('a')])
self.assertEqual(evaluate(ast, Environment()), "foo")
ast = AssignAst(VarAst("a"), LiteralAst("foo"))
with self.assertRaises(Exception):
evaluate(ast, Environment(Environment()))
ast = CallAst(
LambdaAst("", ["a"], VarAst("a")),
[LiteralAst(1)],
)
self.assertEqual(evaluate(ast, Environment()), 1.0)
ast = CallAst(
LambdaAst("", ["a"], VarAst("a")),
[LiteralAst("abc")],
)
self.assertEqual(evaluate(ast, Environment()), "abc")
# (λ loop (n) if n > 0 then n + loop(n - 1) else 0) (10)
ast = CallAst(
LambdaAst(
"loop",
["n"],
IfAst(
BinaryAst(">", VarAst("n"), LiteralAst(0)),
BinaryAst(
"+", VarAst("n"),
CallAst(VarAst("loop"),
[BinaryAst('-', VarAst('n'), LiteralAst(1))])),
LiteralAst(0),
),
), [LiteralAst(10)])
self.assertEqual(evaluate(ast, Environment()), 55.0)
# let (x) x;
ast = LetAst([VarDefAst("x", None)], VarAst("x"))
self.assertEqual(evaluate(ast, Environment()), False)
# let (x = 2, y = x + 1, z = x + y) x + y + z
ast = LetAst([
VarDefAst("x", LiteralAst(2)),
VarDefAst("y", BinaryAst("+", VarAst("x"), LiteralAst(1))),
VarDefAst("z", BinaryAst("+", VarAst("x"), VarAst("y"))),
],
BinaryAst(
"+",
BinaryAst("+", VarAst("x"), VarAst("y")),
VarAst("z"),
))
self.assertEqual(evaluate(ast, Environment()), 10.0)
# the second expression will result an errors,
# since x, y, z are bound to the let body
# let (x = 2, y = x + 1, z = x + y) x + y + z; x + y + z
ast = ProgAst([
LetAst(
[
VarDefAst('x', LiteralAst(2)),
VarDefAst('y', BinaryAst('+', VarAst('x'), LiteralAst(1))),
VarDefAst('z', BinaryAst('+', VarAst('x'), VarAst('y'))),
],
BinaryAst(
'+',
BinaryAst('+', VarAst('x'), VarAst('y')),
VarAst('z'),
),
),
BinaryAst(
'+',
BinaryAst('+', VarAst('x'), VarAst('y')),
VarAst('z'),
),
])
with self.assertRaises(Exception):
evaluate(ast, Environment())
ast = IfAst(
LiteralAst(""),
LiteralAst(1),
None,
)
self.assertEqual(evaluate(ast, Environment()), 1.0)
ast = IfAst(
LiteralAst(False),
LiteralAst(1),
LiteralAst(2),
)
self.assertEqual(evaluate(ast, Environment()), 2.0)
ast = IfAst(
LiteralAst(False),
LiteralAst(1),
LiteralAst(False),
)
self.assertEqual(evaluate(ast, Environment()), False)
ast = {"type": "foo", "value": 'foo'}
with self.assertRaises(Exception):
evaluate(ast, Environment())
def _make_continuation(k: Callable[[Ast], Ast]) -> LambdaAst:
continuation = gensym("R")
return LambdaAst('', [continuation], k(VarAst(continuation)))