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Yacas [Download]
 Yacas (Yet Another Computer Algebra System) is a small and
highly flexible generalpurpose computer algebra language. The
syntax uses a infixoperator grammar parser. The distribution
contains a small library of mathematical functions, but its real
strength is in the language in which you can easily write your
own symbolic manipulation algorithms.
URL: http://www.xs4all.nl/~apinkus/yacas.html
