def A_closure_holds_updateable_values():
def dumb_set(env, sym, val):
env.parent.parent.parent.set(sym[1], val)
def dumb_if_equal(env, val1, val2, then_fn, else_fn):
if val1 == val2:
ret = then_fn
else:
ret = else_fn
return eval_expr(("call", ret, []), env)
env = Env()
env.set("dumb_set", ("native", dumb_set))
env.set("dumb_if_equal", ("native", dumb_if_equal))
assert_that(
evald(
"""
counter = {
x = 0;
{:(meth)
dumb_if_equal(meth, "get",
{x;},
{dumb_set("x", x + 1);}
);
}
}();
counter("inc");
counter("inc");
counter("get");
""",
env
),
equals(("number", 2))
)
def A_native_function_can_edit_the_environment():
def mx3(env):
env.set("x", ("number", 3))
env = Env()
env.set("make_x_three", ("native", mx3))
assert_that(evald("x=1;make_x_three();x;", env), equals(("number", 3)))
def Native_function_gets_called():
def native_fn(env, x, y):
return ("number", x[1] + y[1])
env = Env()
env.set("native_fn", ("native", native_fn))
assert_that(evald("native_fn( 2, 8 );", env), equals(("number", 10)))
def A_native_function_can_edit_the_environment():
def mx3(env):
env.set("x", ("number", 3))
env = Env()
env.set("make_x_three", ("native", mx3))
assert_that(
evald("x=1;make_x_three();x;", env),
equals(("number", 3))
)
def eval_expr(expr, env):
typ = expr[0]
if typ == "number":
return ("number", float(expr[1]))
elif typ == "string":
return ("string", expr[1])
elif typ == "none":
return ("none", )
elif typ == "operation":
return _operation(expr, env)
elif typ == "symbol":
name = expr[1]
ret = env.get(name)
if ret is None:
raise Exception("Unknown symbol '%s'." % name)
else:
return ret
elif typ == "assignment":
var_name = expr[1][1]
if var_name in env.items:
raise Exception("Not allowed to re-assign symbol '%s'." % var_name)
val = eval_expr(expr[2], env)
env.set(var_name, val)
return val
elif typ == "call":
return _function_call(expr, env)
elif typ == "function":
return ("function", expr[1], expr[2], Env(env))
else:
raise Exception("Unknown expression type: " + str(expr))
def compile_(output, filename):
env = Env()
with open(output, "w") as outfile:
outfile.write(
compile_list(parse(lex(pycell.library.as_text(env))), env))
with open(filename, encoding="ascii") as infile:
outfile.write(
compile_list(parse(lex(chars_in_file(infile))), env))
def Wrong_number_of_arguments_to_a_native_function_is_an_error():
def native_fn0(env):
return ("number", 12)
def native_fn3(env, x, y, z):
return ("number", 12)
env = Env()
env.set("native_fn0", ("native", native_fn0))
env.set("native_fn3", ("native", native_fn3))
assert_prog_fails(
"native_fn0(3);",
"1 arguments passed to function ('symbol', 'native_fn0'), but it requires 0 arguments.",
env)
assert_prog_fails(
"native_fn3(3, 2);",
"2 arguments passed to function ('symbol', 'native_fn3'), but it requires 3 arguments.",
env)
def Wrong_number_of_arguments_to_a_native_function_is_an_error():
def native_fn0(env):
return ("number", 12)
def native_fn3(env, x, y, z):
return ("number", 12)
env = Env()
env.set("native_fn0", ("native", native_fn0))
env.set("native_fn3", ("native", native_fn3))
assert_prog_fails(
"native_fn0(3);",
"1 arguments passed to function ('symbol', 'native_fn0'), but it requires 0 arguments.",
env
)
assert_prog_fails(
"native_fn3(3, 2);",
"2 arguments passed to function ('symbol', 'native_fn3'), but it requires 3 arguments.",
env
)
def _function_call(expr, env):
fn = eval_expr(expr[1], env)
args = list((eval_expr(a, env) for a in expr[2]))
if fn[0] == "function":
params = fn[1]
fail_if_wrong_number_of_args(expr[1], params, args)
body = fn[2]
fn_env = fn[3]
new_env = Env(fn_env)
for p, a in zip(params, args):
new_env.set(p[1], a)
return eval_list(body, new_env)
elif fn[0] == "native":
py_fn = fn[1]
params = inspect.getargspec(py_fn).args
fail_if_wrong_number_of_args(expr[1], params[1:], args)
return fn[1](env, *args)
else:
raise Exception(
"Attempted to call something that is not a function: %s" % str(fn))
def A_closure_holds_updateable_values():
def dumb_set(env, sym, val):
env.parent.parent.parent.set(sym[1], val)
def dumb_if_equal(env, val1, val2, then_fn, else_fn):
if val1 == val2:
ret = then_fn
else:
ret = else_fn
return eval_expr(("call", ret, []), env)
env = Env()
env.set("dumb_set", ("native", dumb_set))
env.set("dumb_if_equal", ("native", dumb_if_equal))
assert_that(
evald(
"""
counter = {
x = 0;
{:(meth)
dumb_if_equal(meth, "get",
{x;},
{dumb_set("x", x + 1);}
);
}
}();
counter("inc");
counter("inc");
counter("get");
""", env), equals(("number", 2)))
def _function_call(expr, env):
fn = eval_expr(expr[1], env)
args = list((eval_expr(a, env) for a in expr[2]))
if fn[0] == "function":
params = fn[1]
fail_if_wrong_number_of_args(expr[1], params, args)
body = fn[2]
fn_env = fn[3]
new_env = Env(fn_env)
for p, a in zip(params, args):
new_env.set(p[1], a)
return eval_list(body, new_env)
elif fn[0] == "native":
py_fn = fn[1]
params = inspect.getargspec(py_fn).args
fail_if_wrong_number_of_args(expr[1], params[1:], args)
return fn[1](env, *args)
else:
raise Exception(
"Attempted to call something that is not a function: %s" %
str(fn)
)
def repl(stdin, stdout, stderr):
env = Env(parent=None, stdin=stdin, stdout=stdout, stderr=stderr)
pycell.library.import_(env)
while True:
try:
p = Prompt(stdout)
for value in eval_iter(
parse(lex(p.handle_chars(chars_in_file(stdin)))), env):
p.value(value)
break
except Exception as e:
stderr.write(str(e))
stderr.write("\n")
stdout.write("\n")
stdout.flush()
def runned(inp):
with StringIO() as stdin, StringIO() as stdout:
env = Env(stdin=stdin, stdout=stdout, stderr=stdout)
pycell.library.import_(env)
return eval_list(parse(lex(inp)), env)
def evald(inp, stdout=None):
env = Env(stdout=stdout)
pycell.library.import_(env)
return eval_list(parse(lex(inp)), env)
def None_evaluates_to_None():
assert_that(eval_expr(("none", ), Env()), equals(("none", )))
def run(filename, stdin, stdout, stderr):
env = Env(stdin=stdin, stdout=stdout, stderr=stdout)
pycell.library.import_(env)
with open(filename, encoding="ascii") as f:
eval_list(parse(lex(chars_in_file(f))), env)
def Native_function_gets_called():
def native_fn(env, x, y):
return ("number", x[1] + y[1])
env = Env()
env.set("native_fn", ("native", native_fn))
assert_that(evald("native_fn( 2, 8 );", env), equals(("number", 10)))
def compiled(inp, env=None):
if env is None:
env = Env()
return compile_list(parse(lex(inp)), env)
def evald(inp, env=None):
if env is None:
env = Env()
return eval_list(parse(lex(inp)), env)