Trying to use the fgl unit, specifically the TFPGMap.   Below is a simple program I'm trying to compile; it gives me two errors:

fgl.pp(1582,18) Error: Operator is not overloaded: "pair" < "pair"
fgl.pp(1584,23) Error: Operator is not overloaded: "pair" > "pair"
program test;
{$mode objfpc}
uses
   fgl;
type
    pair = record
       x, y : integer;
    end;
operator < (a,b: pair) r:boolean;
begin
    if a.x < a.y then
       r := true
    else
       r := false;
end;
operator > (a,b: pair) r:boolean;
begin
    if a.x > a.y then
       r := true
    else
       r := false;
end;
function cmp(const a,b : pair) : LongInt;
begin
    if a < b then
       cmp := -1
    else
       if a > b then
          cmp := 1
       else
          cmp := 0;
end;
type
   TMyDict = specialize TFPGMap<pair, integer>;
var
   Dict: TMyDict;
   key: pair;
   Value: Integer;
begin
    Dict := TMyDict.Create;
    Dict.OnKeyCompare := @cmp;
    key.x := 2;
    key.y := 4;
    Dict.Add(key, 99);
    Value := Dict[key];
    writeln(Value);
    Dict.Free;
end.

Any advice appreciated. Thanks.

Pete

El 24/1/24 a les 20:31, ppadilcdx via fpc-pascal ha escrit:

add a {$Modeswitch advancedrecords} and use class operators

program test; {$mode objfpc}

   {$modeswitch advancedrecords}

         class operator < (a,b:pair):boolean;
         class operator > (a,b:pair):boolean;

   end;

operator < (a,b: pair) r:boolean;

    class operator pair.<(a,b:pair):boolean;

begin    if a.x < a.y then       r := true

          result:=true

   else       r := false;

          result:=false;

end;

bye

Thanks for that, now it compiles but it doesn't work, i.e. I added a pair and value and then used trygetdata and it can't find it. So perhaps I'm missing something else :

program test;
{$mode objfpc}
{$modeswitch advancedrecords}
uses
   fgl;
type
    pair = record
       x, y : integer;
       class operator > (a,b: pair) r:boolean;
       class operator < (a,b: pair) r:boolean;
    end;
class operator pair.< (a,b: pair) r:boolean;
begin
    if a.x < a.y then
       r := true
    else
       r := false;
end;
class operator pair.> (a,b: pair) r:boolean;
begin
    if a.x > a.y then
       r := true
    else
       r := false;
end;
function cmp(const a,b : pair) : LongInt;
begin
    if a < b then
       cmp := -1
    else
       if a > b then
          cmp := 1
       else
          cmp := 0;
end;
type
   TMyDict = specialize TFPGMap<pair, integer>;
var
   Dict: TMyDict;
   key: pair;
   Value: Integer;
   flg: boolean;
begin
    Dict := TMyDict.Create;
    Dict.OnKeyCompare := @cmp;
    key.x := 2;
    key.y := 4;
    Dict.Add(key, 99);
    flg := Dict.trygetdata(key, Value);
    writeln(flg);
    writeln(Value);
    Dict.Free;
end.

ppadilcdx via fpc-pascal schrieb am Mi.,
24. Jan. 2024, 22:07:

Thanks for that, now it compiles but it doesn't work, i.e. I added a pair and value and then used trygetdata and it can't find it. So perhaps I'm missing something else :

Your operator needs to establish a true order between the two passed in values. Right now your operators only check a, but not b. That is wrong and thus the map won't work correctly.

Regards,
Sven

Oh I didn't notice the typo, duh.  Thanks!!