TExprFunc Type

Summary

Function type for custom function definition.

Declaration

TExprFunc = procedure(Expr: TExprRec);

Description

Any custome defined function must be of this type to be used in the expression parser.

Example 1

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.Destroy;
         end;
    end;