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October 21, 2017
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Simple Numerical Formula Parser

  • April 5, 2000
  • By Developer.com Staff
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This article was contributed by Ralf Wirtz.

screen shot

Environment: VC6 SP3, Windows 95/98/NT/2000

The class CFormulaParser encapsulates a very useful mathematical parser for analytic/numerical formula transformation.

The formula dialog above is actually not necessary for the functionality but allows you comfortable to put in a formula string.

Hereby an extract from the header file:

class CFormulaParser  
{
private:
 //Implementation
 CString m_strFormula;
 CString m_strFunction;
 CString m_strErrortext;
 double m_dFktValue;
 double m_dFunctionConstant[ANZFUNKTKONST];
 CStringArray m_strStandardFunction;

 double SignFactor(WORD& nPosition, CString& strCharacter);
 double Expression(WORD& nPosition, CString& strCharacter);

 double SimpleExpression(WORD& nPosition, 
                         CString& strCharacter);

 double Term(WORD& nPosition, CString& strCharacter);
 double Factor(WORD& nPosition, CString& strCharacter);
 double Char_n(WORD& nPosition, CString& strCharacter);
				 
public:
 CString GetFormula();
 void SetFormula(CString Formula);
 void SetFunctConst(int index, double val);
	
 CFormulaParser();
 virtual ~CFormulaParser();

//Interface
 double Calculation(CString strFormula, 
                    double xValue, 
                    WORD& 
                    ErrorPosition, 
                    CString& 
                    Errortext);
};

The main method in CFormulaParser for the evaluation is:

double Calculation(CString strFormula, 
                   double xValue, 
                   WORD& 
                   ErrorPosition, 
                   CString& 
                   Errortext);

where

  • strFormula is the formula string, e.g. "b*sin(x)/x"
  • xValue is in this case x, e.g. 3.14 (point instead comma!)
  • ErrorPosition gives back the error position in the string
  • Errortext gives back the corresponding error text

The parser is part of the program SimplexNumerica. For more information, please see my German website http://www.SimplexNumerica.de.

Download

Download demo project (with source) - 104 Kb






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