上記モジュール内の関数。n個の引数なし関数を渡して、全組み合わせができるような、トラックバックが実現できるような、そんなものですがまだよくわかってない。
# conjoin is a simple backtracking generator, named in honor of Icon's # "conjunction" control structure. Pass a list of no-argument functions # that return iterable objects. Easiest to explain by example: assume the # function list [x, y, z] is passed. Then conjoin acts like: # # def g(): # values = [None] * 3 # for values[0] in x(): # for values[1] in y(): # for values[2] in z(): # yield values # # So some 3-lists of values *may* be generated, each time we successfully # get into the innermost loop. If an iterator fails (is exhausted) before # then, it "backtracks" to get the next value from the nearest enclosing # iterator (the one "to the left"), and starts all over again at the next # slot (pumps a fresh iterator). Of course this is most useful when the # iterators have side-effects, so that which values *can* be generated at # each slot depend on the values iterated at previous slots.
