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| class Shift: | |
| def __init__(self, fun): | |
| self.fun = fun | |
| def map(self, f): return Shift(lambda k: self.fun(lambda x: k(f(x)))) | |
| def bind(self, f): return Shift(lambda k: self.fun(lambda x: f(x).fun(k))) | |
| def bind2(self, f): | |
| def aux(k): | |
| def aux1(x): | |
| fx = f(x) | |
| if isinstance(fx, Shift): return fx.fun(k) | |
| return k(fx) | |
| return aux1 | |
| return Shift(lambda k: self.fun(aux(k))) | |
| def reset(c): return c.fun(lambda x: x) | |
| if __name__ == "__main__": | |
| ctx = Shift(lambda k: k(k(k(7)))).bind2(lambda x: x+1) | |
| assert(reset(ctx) == 10) | |
| ctx = Shift(lambda k: k(7)).bind2(lambda x: x+1) | |
| assert(reset(ctx) * 2 == 16) | |
| def f(k): | |
| k(k(k(7))) | |
| return "done" | |
| ctx = Shift(f).bind2(lambda x: x+1) | |
| assert(reset(ctx) == "done") | |
| ctx = Shift(lambda k: k(k(k(7)))).bind2(lambda x: x+1) | |
| assert(reset(ctx) * 2 == 20) | |
| def foo(): return Shift(lambda k: k(k(k(7)))).bind2(lambda x: x+1) | |
| def bar(): return foo().bind2(lambda x: x*2) | |
| def baz(): return reset(bar()) | |
| assert(baz() == 70) # 70 | |
| def foo1(): return Shift(lambda k: k(k(k(7)))).bind2(lambda x: x+1) | |
| def bar1(): return foo1().bind2(lambda x: Shift(lambda k: k(7)).bind2(lambda y: x+y)) | |
| def baz1(): return reset(bar1()) | |
| assert(baz1() == 31) # 31 | |
| def foo2(): return Shift(lambda k: k(k(7))).bind2(lambda x: x+1) | |
| def bar2(): return foo2().bind2(lambda x: foo2().bind2(lambda y: x+y)) | |
| def baz2(): return reset(bar2()) | |
| assert(baz2() == 61) # 61 |
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