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Magic function is a special function used in following cases

•number of parameters can vary

•Parameter types are not known

•parameter cannot be passed in a standard way (for example - array)

•function needs Scripter instance to work.

•function has var parameters (for example Insert or Delete)

 

Magic function has following declaration:

 

function MagicFunction(const Sender: TScriptParser; var Params: TScriptStack; 
  StackTop, ParamCount: integer): Variant;

 

Sender is Scripter instance in which function is called.

Params is pointer to current runtime stack (array of TExVariable)

StackTop is index of top stack variable

ParamCount - number of parameters in call.

 

Example of magic function implementation:

 

function MagicInc(const Sender: THtScriptParser; var Params: TScriptStack; 

  StackTop, ParamCount: integer): Variant;
begin
  if ParamCount = 1 then
  begin
    if Params[StackTop].IsTemp then
      Sender.Tokenizer.Error(sVarRequiredforInc);
    Result := Params[StackTop].Value + 1;
    Params[StackTop].Value := Result;
  end else begin
    if Params[StackTop - 1].IsTemp then
      Sender.Tokenizer.Error(sVarRequiredforInc);
    Result := Params[StackTop - 1].Value + Params[StackTop].Value;
    Params[StackTop - 1].Value := Result;
  end;
end;

 
Registering magic function:

 

  HtScriptGlobal.RegisterMagicFunc('Inc', MagicInc);

 

Getting function name.

 

When magic function is registered with different names, current (called) function name can be obtained via call stack:

 

 Name := TScriptFunc(Sender.DebugStack[Sender.DebugStack.Count - 1]).Name