Created
June 20, 2016 14:13
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from inspect import isgenerator | |
def fact(n): | |
if n <= 1: | |
return n | |
else: | |
f = yield fact(n-1) | |
return f * n | |
def fib(n): | |
if n <= 1: | |
return n | |
else: | |
f_1 = yield fib(n-1) | |
f_2 = yield fib(n-2) | |
return f_1 + f_2 | |
def xfib(n): | |
if n <= 1: | |
return n | |
else: | |
f_1 = yield from xfib(n-1) | |
f_2 = yield from xfib(n-2) | |
return f_1 + f_2 | |
def fn(gen): | |
return cons(None, cons(gen, none())) | |
def none(): | |
return () | |
def cons(x, xs): | |
return (x, xs) | |
def head(xs): | |
return xs[0] | |
def rest(xs): | |
return xs[1] | |
def empty(xs): | |
return xs == none() | |
def run(xs): | |
if empty(xs): return xs | |
val, gens = xs | |
if empty(gens): return xs | |
ret = go(head(gens), val) | |
if isgenerator(ret): | |
return cons(None, cons(ret, gens)) | |
else: | |
return cons(ret, rest(gens)) | |
def go(gen, val): | |
try: | |
return gen.send(val) | |
except StopIteration as e: | |
return e.value | |
def inspect_run(gen): | |
f = fn(gen) | |
while not empty(rest(f)): | |
print("run {} <- {}".format(head(rest(f)), head(f))) | |
f = run(f) | |
print("return {} by {}".format(head(f), gen)) | |
if __name__ == "__main__": | |
inspect_run(fact(4)) | |
inspect_run(fib(4)) | |
inspect_run(xfib(4)) |
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