import itertools as _itertools

class Amb(object):
    def __init__(self):
        self._names2values   = {}       
        self._func           = None     
        self._valueiterator  = None     
        self._funcargnames   = None     

    def __call__(self, arg=None):
        if hasattr(arg, '__code__'):                
            
            
            
            globls = arg.__globals__ if hasattr(arg, '__globals__') else arg.func_globals
            
            argv = arg.__code__.co_varnames[:arg.__code__.co_argcount]
            for name in argv:
                if name not in self._names2values:
                    assert name in globls, \
                           % name
                    self._names2values[name] = globls[name]
            
            valuesets = [self._names2values[name] for name in argv]
            self._valueiterator = _itertools.product(*valuesets)
            self._func = arg
            self._funcargnames = argv
            return self
        elif arg is not None:
            
            
            
            arg = frozenset(arg)
            return arg
        else:
            
            
            
            return self._nextinsearch()

    def _nextinsearch(self):
        arg = self._func
        globls = arg.__globals__
        argv = self._funcargnames
        found = False
        for values in self._valueiterator:
            if arg(*values):
                
                found = True
                for n, v in zip(argv, values):
                    globls[n] = v
                break
        if not found: raise StopIteration
        return values

    def __iter__(self):
        return self

    def __next__(self):
        return self()
    next = __next__ 

if __name__ == '__main__':
    if True:
        amb = Amb()

        print()
        x = amb(range(1,11))
        y = amb(range(1,11))
        z = amb(range(1,11))

        for _dummy in amb( lambda x, y, z: x*x + y*y == z*z ):
            print ('%s%s%s'% (x, y, z))


    if True:
        amb = Amb()

        print()
        w1 = amb([, , ])
        w2 = amb([, , ])
        w3 = amb([, , ])
        w4 = amb([, ])

        for _dummy in amb( lambda w1, w2, w3, w4: \
                             w1[-1] == w2[0] and \
                             w2[-1] == w3[0] and \
                             w3[-1] == w4[0] ):
            print ('%s%s%s%s'% (w1, w2, w3, w4))

    if True:
        amb = Amb()

        print(
            )
        x = amb([1, 2, 3])
        y = amb([4, 5, 6])

        for _dummy in amb( lambda x, y: x * y != 8 ):
            print ('%s%s'% (x, y))