TMtxExpression.DefineDouble Method

TMtxExpression Class

function DefineDouble(const AVarName: string): TDoubleValue;

Defines new double variable.

#NameTypeDescription
1AVarNamestring

Returns: TDoubleValue

Remarks:

If variable with name AVarName already was definded, it will be redefined and all expressions which contain the symbol AVarName will be recompiled before the next evaluation.

Examples
uses MtxParseExpr, MtxParseClass;

procedure Example(MyParser: TMtxExpression);
var x,y: TDoubleValue;
res: double;
begin
    // 1. Define variables
    x := MyParser.DefineDouble('x');
    y := MyParser.DefineDouble('y');

    // 2. Set values
    x.DoubleValue := 3.0;
    y.DoubleValue := 4.0;

    // 3. Add formula and evaluate,
    MyParser.AddExpr('Sqrt(x*x+y*y)');
    res := MyParser.EvaluateDouble;
    // res = 5.0
end;
See Also: TMtxExpression.Undefine, TMtxExpression.VarByName, TMtxExpression.GetVarList, TMtxExpression.DefineVariable, TMtxExpression.DefineComplex, TMtxExpression.DefineVector, TMtxExpression.DefineMatrix, TMtxExpression.DefineFunction, TMtxExpression.DefineVaryingFunction, TMtxExpression.DefineOperator, TMtxExpression.DefineDoubleConstant, TMtxExpression.DefineComplexConstant