JCL TEvaluator Usage

General Help
1

I am using the JCL TCompiledEvaluator (unit JclExprEval) but am having great difficulty trying to add a user function. I want to add a function of type TUnary32Func (1 parameter) but I cannot figure this out. Unfortunately, I cannot find any JCL documentation on this and the Google Ai assistant presents a number of conflicting and possibly bogus solutions.

The procedure call looks like this but I don’t know how to go any further successfully.

public procedure AddFunc(const AName: string; AFunc: TUnary32Func); overload;

Is there a working example anywhere?

Thanks, Gerard Hook

2

Hi Gerard

I don’t have an answer for you but have you considered DelphiWebScript.

Regards
Graeme

3

Thanks Graeme.

I will have a look.

Regards, Gerard Hook

4

Have a look at your $(BDSCatalogRepository)\JEDICodeLibraryJCL-13\2025.10\examples\common\expreval\ExprEvalExample.dproj, it gives use cases of
procedure TEasyEvaluator.AddFunc(const AName: string; AFunc: TUnary80Func);

5

Thanks Didier.

I see that the AddFunc calls are in the unit ExprEvalExampleLogic (from within the ExprEvalExample). It seems that the functions have to be stand alone and not a member of a class.

I got my test case to work.

Thanks again, Gerard Hook

6

Correct, most of the methods of that example are declared in the JclMath.pas unit.
But if you want to play with methods (ie class procedures /functions), then you could be using the Delphi new RTTI library: eg, for accessing the method → TRttiType.GetMethod, and for invoking it → TRttiMethod.Invoke.. unless you are stick with the JCL Expression Evaluator

7

To be more precise about your question that was:

You have to inspect what the AFunc: TUnary32Func parameter actually is.. It is defined as:
TUnary32Func = function(X: TFloat32): TFloat32;
..which means it is a function pointer, not a method pointer (or a method of an object’s instance), as you wanted it to be.
Note a method pointer would have been declared with the of object identifier.
See the Procedural Types DocWiki