How to build a const array?

Question

I use an interpreter, and one of the functions that my interpreter will support is similar to Delphi Format. In fact, I implement my function using SysUtils.Format. However, I can not create a second parameter to the function array of TVarRec.

Suppose I have the following code. At the moment, I'm just guessing what variables Delphi should have access to the interpreted code ( iVar1and iVar2), but I still do not know how to put them into a structure that is required Format( arFormatArgs).

type TFormatArgs = array of TVarRec;

procedure RunInterpretedFormatFunction;
var
  iMyAge: integer;
  iMyIQ: integer;
  sCode: string;
  sText: string;
begin
  iMyAge := 5;
  iMyIQ := -5;
  sCode := 'Format(''My age is %d and my IQ is %d'', [iMyAge, iMyIQ])';
  sText := FormatThis(sCode, iMyAge, iMyIQ);
end;

function FormatThis(sFormatCode: string; iVar1: integer; iVar2: integer): string;
var
  sFormatString: string;
  arFormatArgs: TFormatArgs;
begin
  sFormatString := GetFormatString(sFormatCode); // I can implement this function
  arFormatArgs := ConstructFormatArgs(iVar1, iVar2); // NEED HELP HERE!
  result := SysUtils.Format(sFormatString, arFormatArgs);
end;

How can I implement my function ConstructFormatArgsin Delphi (not Assembly)?

Answer 1

const , , .. . , .

, Delphi , , const TVarRec.

A TVarRec - :

TVarRec = record
  case Byte of
    vtInteger:    (VInteger: Integer; VType: Byte);
    vtBoolean:    (VBoolean: Boolean);
    vtChar:       (VChar: Char);
    vtExtended:   (VExtended: PExtended);
    vtString:     (VString: PShortString);
    vtPointer:    (VPointer: Pointer);
    vtPChar:      (VPChar: PChar);
    vtObject:     (VObject: TObject);
    vtClass:      (VClass: TClass);
    vtWideChar:   (VWideChar: WideChar);
    vtPWideChar:  (VPWideChar: PWideChar);
    vtAnsiString: (VAnsiString: Pointer);
    vtCurrency:   (VCurrency: PCurrency);
    vtVariant:    (VVariant: PVariant);

TVarRec VType.

, const, , Format():

('% s - ,% d - , [' string ', 10]);

const . :

 procedure VarArraySample( AVarArray : array of const );
  var
    i : integer;
  begin
    for i := 0 to High(AVarArray) do
      do_something;
  end;

High() .

TVarRec. - Delphi . TVarRec :

function VarRecToStr( AVarRec : TVarRec ) : string;
  const
    Bool : array[Boolean] of string = ('False', 'True');
  begin
    case AVarRec.VType of
      vtInteger:    Result := IntToStr(AVarRec.VInteger);
      vtBoolean:    Result := Bool[AVarRec.VBoolean];
      vtChar:       Result := AVarRec.VChar;
      vtExtended:   Result := FloatToStr(AVarRec.VExtended^);
      vtString:     Result := AVarRec.VString^;
      vtPChar:      Result := AVarRec.VPChar;
      vtObject:     Result := AVarRec.VObject.ClassName;
      vtClass:      Result := AVarRec.VClass.ClassName;
      vtAnsiString: Result := string(AVarRec.VAnsiString);
      vtCurrency:   Result := CurrToStr(AVarRec.VCurrency^);
      vtVariant:    Result := string(AVarRec.VVariant^);
    else
      result := '';
    end;
  end;

, const :

function VarArrayToStr( AVarArray : array of const ) : string;
  var
    i : integer;
  begin
    result := '';
    for i := 0 to High(AVarArray) do
      result := result + VarRecToStr( AVarArray[i] );
  end;

Format(). Format() % % something const, .

Answer 2

, array of const array of TVarRec. , , , .

TVarRec - , , . , VType, , . . VType, , VInteger VString.

, , VVariant VInt64. , , , , , Format.

- . VAnsiString VInterface. , , , AnsiString IUnknown, .

, , , , . , const. , Unicode Format JCL. , . , , .

, , . , Delphi .

Answer 3

Found this code https://groups.google.com/forum/#!topic/borland.public.delphi.objectpascal/-xb6O0qX2zc

procedure test(numArgs:integer; MyFormattingString:string);    
var
  v:array of tvarrec;
  i:integer;
begin
  setlength(v, numArgs);
  for i:=1 to numArgs do
  begin
    v[i-1].vtype:=vtpchar;
    v[i-1].vtpchar:=strnew(pchar(myDataSet.FieldByName(inttostr(i)).asstring));
  end;
  memo1.lines.add(Format(MyFormattingString,v);
  for i:=1 to numArgs do strdispose(v[i-1].vtpchar);
end;

It doesn’t answer all that I have to deal with, but I think I know how to build a TVarRec array now.