EvaliN

How to use:
When an expression is passed to LoadFromEpression the list of variables is being initialised with variable names. Before the Evaluate is called the array of IVariables has to being initialised with the values of the variables. Use Variables->IndexOf(VarName) to identify the index of variables. The Functions have to be predefined. If no variables is expected when the constructor can be called as TSOperatio(NULL, NULL, Function, NULL). If the functions are not in the expression call TSOperatio(NULL, NULL, NULL, NULL).
Note that the variables list is in the upper case.

const short // operators
    fPlus       = 1,
    fMinus    = 2,
    fMultiply = 3,
    fDivide    = 4,
    fFunction = 5,
    fExt         = 6;
const short // functions
    fNone = 0,
    fAbs = 1,
    fCos = 2,
    fSin = 3,
    fDefined = 4; // defined by an external program

typedef double (*TEvaluate)(double P1, double P2); //an external function

class TSOperation

{
protected:
    TSOperation *ToCalc; // if evaluable == true the these are in use
    TSOperation *Left, *Right;
    short Function;
    double Value;
    void Calculate();
    void SSCalculate();
    void MDCalculate();
    int VariableIndex;
    TSOperation *Parent;
    TEString FExp;
public:
    double *IVariables;
    TEStringList *Variables, *Functions;

    TSOperation(TSOperation *P, TEStringList *Vars, TEStringList *Funcs, double *IVariables);
     ~TSOperation();
    TEvaluate *Evaluator;
    bool Expandable;
    TEString Func, Param;
    short Operation;
    double P1, P2;

    double Evaluate();
    int LoadFromExpression(const TEString &Exp);
};