Example

Custom function definition taking a single parameter stored at Args[0]. The second parameter (if present) would be stored at Args[1] and so on...

procedure _log10x(Param: TExprRec); begin with Param, Res do begin Complex := Args[0].Complex; if Complex then PCValue^ := Log10(Args[0].PCValue^) else PValue^ := Log10(Args[0].PValue^); end; end; var ep: TMtxExpression; begin ep := TMtxExpression.Create; try ep.DefineFunction('Log10x',_log10x,1); ep.Add('Log10x(1.2)+3'); Label1.Caption := SampleToStr(ep.Evaluate); finally ep.Free; end; end;