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Thomas Capricelli, 11/22/2009 02:09 AM

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h1. Description
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Symia is a piece of software that helps programmers to perform "symbolic computation":http://en.wikipedia.org/wiki/Symbolic_computation, also known as *symbolic calculs*. The main characteristics are
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* Symia is a library : the target audience is programmers.
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* Symia is written in C++.
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* Symia is released under the "GNU Lesser General Public License":http://en.wikipedia.org/wiki/LGPL, so that even close-source software can make use of it.
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* Symia uses "unit tests":http://en.wikipedia.org/wiki/Unit_testing as a mean to prevent regression, to ensure robustness, and to provide working examples that the user can rely on.
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The only other C++ library we are aware of is "Ginac":http://en.wikipedia.org/wiki/GiNaC, which is released under the "GNU General Public License":http://en.wikipedia.org/wiki/Gpl, which prevent it from being used in the industry.
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Symia is far from being able to do as much as, say, Maple or Ginac, but if your needs are basic, you can rely on the robust and "tested":http://en.wikipedia.org/wiki/Unit_testing Symia library.
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Symia is developed and released by "Sylphide Consulting":http://www.sylphide-consulting.com. If you need some more features in Symia, you can either abandon the idea of using Symia, implement the missing features by yourself (and provide the code back, as the "GNU LGPL":http://en.wikipedia.org/wiki/LGPL says), or pay someone to do the job. Of course, *Sylphide Consulting* is an obvious choice for such a task, and we would be delighted if you "contact us":http://www.sylphide-consulting.com/contact about it.
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h1. Design
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Quite simple and classical, see the "class diagram":http://labs.freehackers.org/embedded/symia/inherits.html
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h1. Examples
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The following code highlights the most important features of Symia.
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<pre><code class="c">
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{
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    Expression x("x"), y("y"), a("a"), b("b"), c("c"); // create symbols
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    // Operators and most classical functions are overloaded, so you can construct
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    // complex expressions the way you expect to.
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    Expression e = a*x+b*x*x*exp(-c*(x+1)/(x*x));
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    // Helpers are provided to display an expression
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    QString e_as_text = e.toString(); 
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    // now e_as_text is "a*x+b*x*x*exp(-c*(x+1)/(x*x))"
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    // You can substitute an whole expression to any symbol
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    e = e.replace(x, b+log(c))
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    // e now is "a*(b+log(c))+b*(b+log(c))*(b+log(c))*exp(-c*(b+log(c)+1)/((b+log(c))*(b+log(c))))"
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    // yes, this is ugly, and this is the reason what you are happy a computer handles that for you.
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    // Evaluation is about using replace() as well
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    e = e.replace(a,-3).replace(c,1).replace(b,.78);
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    // e now is "-2.31455"
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}
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</code></pre>
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h1. Frequently Asked Questions
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Where does the name come from ? This is short for *symbolia*, which has already too much hits in google.