[SOLVED] Declare operator in Delphi mode

[Okoba]

How can I declare an operator in Delphi mode?
in ObjFPC it is like this:

Code: Pascal  [Select][+][-]

1.   operator := (r: Real) z: complex;
2.   begin
3.     z.re := r;
4.     z.im := 0.0;
5.   end;      

As documented here, I should use the operator name like this:

Code: Pascal  [Select][+][-]

1.   operator assign (r: Real) z: complex;
2.   begin
3.     z.re := r;
4.     z.im := 0.0;
5.   end;

So why the compiler gives error on this code?

project1.lpr(12,12) Fatal: Syntax error, "=" expected but "identifier ASSIGN" found

Code: Pascal  [Select][+][-]

1. program Project1;
2.  
3. {$MODE Delphi}
4.  
5.  
6. type
7.   complex = record
8.     re: Real;
9.     im: Real;
10.   end;
11.  
12.   operator assign (r: Real) z: complex;
13.   begin
14.     z.re := r;
15.     z.im := 0.0;
16.   end;
17.  
18. var
19.   R: Real;
20.   C: complex;
21.  
22. begin
23.   C := R;
24. end.            

It is also not possible to declare operators for simple types like integer or string in Delphi mode.

Code: Pascal  [Select][+][-]

1. program Project1;
2.  
3. {$mode delphi}
4.  
5.   operator := (a: Integer) s: String; //Error
6.   begin
7.   end;
8.  
9. begin
10. end.                        

[Bart]

See https://wiki.freepascal.org/Operator_overloading

It states: "In {$mode Delphi}, operator overloading can only be done in the context of classes or advanced records "

Your type complex is neither.

Bart

[Okoba]

I saw this, but I thought the actual FPC document is the true reference, and I could not find that statement in there.
So there is no way to declare an operator for a simple type like integer in Delphi mode? Just for records and classes and in their context?

[Bart]

AFAIK not, because that would be Delphi incompatible.
So, either make it a class or an advanced record, or use mode objfpc, where you can benefit from the ease of overloading operators (we are better than Delphi!).

Bart

[Okoba]

I like to use objfpc but it has its own problems like needing specializing every generic method for every use: https://forum.lazarus.freepascal.org/index.php/topic,52007

[Bart]

Make it an advanced record then, the operators will be part of the type definition IIRC.

Bart

[Okoba]

Yes, if it is a record, I can do that. But for simple types like integer or string, it is not possible.
Should I report a bug to update the FPC document to show this limitation in the Delphi mode?

[Bart]

If the official docs don't mention it, by all means do.
Or ask on fpc-devel mailinglist before doing so, it may already have been fixed in trunk.

Bart

[jamie]

In delphi mode you use "implicit" instead of the ":="

Btw, the is already a complex unit in the libs.

I can't remember the name off. "Ucomplex" maybe?

[Bart]

In delphi mode you use "implicit" instead of the ":="

If so, then the wiki page is wrong.
The offical docs say you can use assigment operators and/or implicit/explicit operators.

Btw, the is already a complex unit in the libs.

I can't remember the name off. "Ucomplex" maybe?

Yes, its unit uComplex.

I gathered TS was just playing around with operator overloading and use a complex type as an example.

Bart

[Okoba]

@Bart, yes and I updated the question.
BTW, I checked with trunk so it is not fixed.

[PascalDragon]

I saw this, but I thought the actual FPC document is the true reference, and I could not find that statement in there.

The FPC documentation being the true reference does not necessarily mean that it is complete and/or bug free. Please file a bug against the documentation.

So there is no way to declare an operator for a simple type like integer in Delphi mode? Just for records and classes and in their context?

Nearly correct: only records support operators (in either mode).

Also as a solution you can put your type and the operator overloads into a separate unit compiled in mode ObjFPC and use it in a unit with mode Delphi. Cause the operator resolution does not depend no the mode (the only exception is the +-operator for dynamic arrays which depends on the modeswitch ArrayOperators).

I like to use objfpc but it has its own problems like needing specializing every generic method for every use: https://forum.lazarus.freepascal.org/index.php/topic,52007

Correction: you need to write the specialize keyword every time. But the specialization itself is handled the same in both modes.

@Bart, yes and I updated the question.
BTW, I checked with trunk so it is not fixed.

The only fix necessary is a fix for the documentation. That global operators are not allowed in mode Delphi is by design and choice. Please file a bug report for the documentation, so that this is cleared up.

[Okoba]

Thanks for clarification.
Here is the bug: https://bugs.freepascal.org/view.php?id=38071

[Bart]

Thanks for clarification.
Here is the bug: https://bugs.freepascal.org/view.php?id=38071

You beat me by a few seconds.

Bart

[Okoba]

That's a pleasure