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A powerful function parser

, 22 Feb 2000 123.9K 1.9K 58
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A simple yet powerful function parser that parses and evaluates standard mathematical functions
  • Download source files - 82 Kb
  • The inspiration to write this code was to have an easy-to-use parser for functions given as string. You have a string like "cos(x)-7*x/(1+x)", and you want to compute some values, maybe for displaying the graph of the function. You can write code like this:

    CFunction<long double>* fkt = CFunction<long double>::Parse("cos(x)-7*x/(1+x)");
    long double y = fkt->Execute(1.5);

    There are lots of definitions in the background, but the result is easy and fast! There is a one-time pasing step to construct the function tree, and function evaluations are only calls of standard math functions like sin, +, *, sqrt. When you want to know details about the implementaion, you should look into the source code. It would be too complex to describe the parsing algorithm here.

    License

    This article has no explicit license attached to it but may contain usage terms in the article text or the download files themselves. If in doubt please contact the author via the discussion board below.

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    About the Author

    Andreas Jäger
    Web Developer
    Germany Germany
    No Biography provided

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    Comments and Discussions

     
    GeneralMFC compile Pin
    Luke Murphey6-Jul-02 9:28
    memberLuke Murphey6-Jul-02 9:28 
    I am working on a port of UNIX Xspread to windows. I am attempting to integrate this code into my MFC application, however, I cannot get it to compile. Below is the code snippet intended to get the result:

    CString Expression;

    //Call the math parser, get the function result and set the cell value to the result
    CFunction* bob = CFunction::Parse(m_strText);
    Expression = bob->GetName();


    Note: when I post this message to this site, the template prefix argument keeps disappearing (strange). CFunction has a template argument of long double (so does the scope for the call to Parse). This is OK in my application.

    Here is the errors:

    C:\My Documents\MyProjects\Xspread32\xspread32\Grid_src\GridCell.cpp(212) : error C2065: 'CFunction' : undeclared identifier
    C:\My Documents\MyProjects\Xspread32\xspread32\Grid_src\GridCell.cpp(212) : error C2062: type 'long double' unexpected
    C:\My Documents\MyProjects\Xspread32\xspread32\Grid_src\GridCell.cpp(212) : error C2039: 'Parse' : is not a member of '`global namespace''
    C:\My Documents\MyProjects\Xspread32\xspread32\Grid_src\GridCell.cpp(213) : error C2065: 'bob' : undeclared identifier
    C:\My Documents\MyProjects\Xspread32\xspread32\Grid_src\GridCell.cpp(213) : error C2227: left of '->GetName' must point to class/struct/union


    I did include the header files, and the IDE does display that the object "func" is a CFunction object (i.e. when you hover the cursor over the object name in MVC++ 6). I just can't make a connnection between my code and this math parser. I downloaded the command line code and it compiles with no problems. I created a new MFC project and tried to integrate the parser in the same manner as the console code that worked & I got the same errors. I am relatively new to MFC (not new to C++ however) and I could use any help I can get.

    Luke
    GeneralRe: MFC compile Pin
    lLukeMurphey8-Jul-02 6:56
    memberlLukeMurphey8-Jul-02 6:56 

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