Comment #1 on issue 1601 by asmeurer: match trouble and tutorial
http://code.google.com/p/sympy/issues/detail?id=1601

Yep, this is pretty much what I saw when I stepped through it in the  
debugger.  It seems like there should be a
way for the pattern to check to see if it can still match the x to b after  
matching sin(x) in (4), instead of just
throwing it out.  Thanks for pointing out .as_independent().  I was writing  
my own function that did that for
another part of my code.

Also, I think args are ordered based on hash values, whereas printing is  
based on Basic._compare_pretty.  So they
are not necessarily reverse of each other (args ordering can be different  
on different machines that compute
hashes differently).

Maybe you should convert this into a Sphinx doc and put it in the docs.  It  
would have been nice to have
whenever I was trying to figure out how match works.

I searched for papers on matching mathematical expressions and found:
http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.36.139

Maple's docs don't cite any papers for their pattern matching.

I wonder, how do other open-source CAS's do it?

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