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March 8, 2002
8:46 a.m.
I confess I admire the a**T suggestion for a notation for transpose(a). The question was raised as to whether this really works and an empirical proof was offered that it does. Here is how it works. In a**T the first thing tried is to ask a.__pow__ if it can manage with T as an argument. The array says, hmm, T is an instance of a class that I never heard of, and it doesn't have an __array__ attribute to call in order to make it an array. I pass. Then T's class' __rpow__ is given a turn, and asked if it can do the job with a as an argument, which it can. This is how 2**a works, or 2 - a, too. The int type disavows any knowledge of what to do, so the other operand gets a chance to save the day. So this is a "trick" we use every day.
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Paul F Dubois