Re: [fpc-pascal] Incompatible type for generics?

2013-09-24 Thread Xiangrong Fang 
I know it is same but why no error on the line:

for n in sm1.reversed...

regards.
在 2013-9-24 下午11:23，"Sven Barth" 写道：

>  Am 24.09.2013 17:14, schrieb Xiangrong Fang:
>
>  2013/9/24 Sven Barth 
>
>
>> How is PNode declared? What is the exact error?
>>
>>
>  PNode is declared inside TTreap generic class, the source is here:
>
> https://github.com/xrfang/fpcollection/blob/master/src/units/treap.pas
>
>  The exact error is:
>
> Error: Incompatible types: got
> "TStringMapper.TTreap$AnsiString$AnsiString" expected "TStringMapper"
>
> The error is exactly the same as the one in your TIntTree, because the
> return type of TTreap.Reversed is TTreap
> and nothing else. Thus the solution is the same as for TIntTree.Next:
> either none or a new "Reversed" function. And again: This problem would
> also occur with non generic classes.
>
> Regards,
> Sven
>
> ___
> fpc-pascal maillist  -  fpc-pascal@lists.freepascal.org
> http://lists.freepascal.org/mailman/listinfo/fpc-pascal
>
___
fpc-pascal maillist  -  fpc-pascal@lists.freepascal.org
http://lists.freepascal.org/mailman/listinfo/fpc-pascal

Re: [fpc-pascal] Incompatible type for generics?

2013-09-24 Thread Sven Barth 

Am 24.09.2013 17:32, schrieb Xiangrong Fang:


I know it is same but why no error on the line:

for n in sm1.reversed...

n is of type TStringMapper.PNode whereby PNode is declared inside 
TTreap and thus the type is in reality a TTreapString>.
sm1.reversed returns a TTreap which has an enumerator 
that works on a TTreap.PNode. So everything is well.


Regards,
Sven
___
fpc-pascal maillist  -  fpc-pascal@lists.freepascal.org
http://lists.freepascal.org/mailman/listinfo/fpc-pascal

Re: [fpc-pascal] Incompatible type for generics?

2013-09-24 Thread Sven Barth 

Am 24.09.2013 17:14, schrieb Xiangrong Fang:
2013/9/24 Sven Barth >


How is PNode declared? What is the exact error?


PNode is declared inside TTreap generic class, the source is here:

https://github.com/xrfang/fpcollection/blob/master/src/units/treap.pas

The exact error is:

Error: Incompatible types: got 
"TStringMapper.TTreap$AnsiString$AnsiString" expected "TStringMapper"
The error is exactly the same as the one in your TIntTree, because the 
return type of TTreap.Reversed is TTreap 
and nothing else. Thus the solution is the same as for TIntTree.Next: 
either none or a new "Reversed" function. And again: This problem would 
also occur with non generic classes.


Regards,
Sven
___
fpc-pascal maillist  -  fpc-pascal@lists.freepascal.org
http://lists.freepascal.org/mailman/listinfo/fpc-pascal

Re: [fpc-pascal] Incompatible type for generics?

2013-09-24 Thread Xiangrong Fang 
2013/9/24 Sven Barth 


> How is PNode declared? What is the exact error?
>
>
PNode is declared inside TTreap generic class, the source is here:

https://github.com/xrfang/fpcollection/blob/master/src/units/treap.pas

The exact error is:

Error: Incompatible types: got "TStringMapper.TTreap$AnsiString$AnsiString"
expected "TStringMapper"
___
fpc-pascal maillist  -  fpc-pascal@lists.freepascal.org
http://lists.freepascal.org/mailman/listinfo/fpc-pascal

Re: [fpc-pascal] Incompatible type for generics?

2013-09-24 Thread Sven Barth 

Am 24.09.2013 15:50, schrieb Xiangrong Fang:

Hi Sven,

2013/9/23 Xiangrong Fang mailto:xrf...@gmail.com>>

Short answer: you can't. The same would happen with normal
classes.

Long answer: You could add an additional method "Next" to your
"TIntTree" which returns a "TIntTree" and just do "Result :=
TIntTree(inherited Next);" there.

I still have problem with this strange issue.   See the demo program 
below:


program test;
{$mode objfpc}{$H+}
uses treap;
type
  TStringMapper = class(specialize TTreap)
  end;
var
  sm1, sm2: TStringMapper;
  n: TStringMapper.PNode;
begin
  sm1 := TStringMapper.Create;
  for n in sm1.Reversed do WriteLn(n^.Key);   <-- but NOT here
  sm2 := sm1.Reversed;<-- error here
end.

How is PNode declared? What is the exact error?
Why is this?  Also, I found that the keyword "specialize" is 
recognized in fpc mode, but "class" is only valid in objfpc mode, is 
that correct?
"specialize" is used in all modes except mode Delphi for 
specializations. "class" is available in all modes except "iso", "tp" 
and "fpc", but can be enabled there using {$modeswitch class}.


Regards,
Sven

___
fpc-pascal maillist  -  fpc-pascal@lists.freepascal.org
http://lists.freepascal.org/mailman/listinfo/fpc-pascal

Re: [fpc-pascal] Incompatible type for generics?

2013-09-24 Thread Xiangrong Fang 
Hi Sven,

2013/9/23 Xiangrong Fang 

>  Short answer: you can't. The same would happen with normal classes.
>>
>> Long answer: You could add an additional method "Next" to your "TIntTree"
>> which returns a "TIntTree" and just do "Result := TIntTree(inherited
>> Next);" there.
>>
> I still have problem with this strange issue.   See the demo program below:

program test;
{$mode objfpc}{$H+}
uses treap;
type
  TStringMapper = class(specialize TTreap)
  end;
var
  sm1, sm2: TStringMapper;
  n: TStringMapper.PNode;
begin
  sm1 := TStringMapper.Create;
  for n in sm1.Reversed do WriteLn(n^.Key);   <-- but NOT here
  sm2 := sm1.Reversed;<-- error here
end.

Why is this?  Also, I found that the keyword "specialize" is recognized in
fpc mode, but "class" is only valid in objfpc mode, is that correct?

Regards,
Xiangrong
___
fpc-pascal maillist  -  fpc-pascal@lists.freepascal.org
http://lists.freepascal.org/mailman/listinfo/fpc-pascal

Re: [fpc-pascal] Incompatible type for generics?

2013-09-23 Thread Xiangrong Fang 
> Short answer: you can't. The same would happen with normal classes.
>
> Long answer: You could add an additional method "Next" to your "TIntTree"
> which returns a "TIntTree" and just do "Result := TIntTree(inherited
> Next);" there.
>
> Why are you subclassing in this case anyway?
>
Thanks, I will inherit the method.  I need to add features in the
sub-class. This empty TIntTree is just to show the problem.
___
fpc-pascal maillist  -  fpc-pascal@lists.freepascal.org
http://lists.freepascal.org/mailman/listinfo/fpc-pascal

Re: [fpc-pascal] Incompatible type for generics?

2013-09-23 Thread Sven Barth 
Am 23.09.2013 09:10 schrieb "Xiangrong Fang" :
>
> Hi All,
>
> I wrote a TTree generic class, the code is here:
>
> https://github.com/xrfang/fpcollection/blob/master/src/units/tree.pas
>
> While using this class, I encountered the following problem:
>
> program project1;
> {$mode objfpc}{$H+}
> uses tree;
> type
>   TIntTree = class(specialize TTree)
>   end;
> var
>   ti : TIntTree;
> begin
>   ti := TIntTree.Create(1, nil);
>   ti := ti.Next;  <-- error here
> end.
>
> The error message is:
>
> Error: Incompatible types: got "TIntTree.TTree$LongInt" expected
"TIntTree"
>
> If I do not inherit TTree but just specialize it, there is no error.
>
> How can I solve this problem so that I don' t have to use typecast
everywhere?

Short answer: you can't. The same would happen with normal classes.

Long answer: You could add an additional method "Next" to your "TIntTree"
which returns a "TIntTree" and just do "Result := TIntTree(inherited
Next);" there.

Why are you subclassing in this case anyway?

Regards,
Sven
___
fpc-pascal maillist  -  fpc-pascal@lists.freepascal.org
http://lists.freepascal.org/mailman/listinfo/fpc-pascal