[fpc-pascal] FPImage and GetDataLineStart

[Sven Barth]

On 22.04.2011 12:18, Florian Klämpfl wrote:
> Am 22.04.2011 12:06, schrieb michael.vancanneyt at wisa.be:
>>
>>
>> On Fri, 22 Apr 2011, Florian Klämpfl wrote:
>>
>>>> mya.pp(16,12) Error: Operator is not overloaded: "complex" + "complex"
>>>> myb.pp(9,14) Fatal: There were 1 errors compiling module, stopping
>>>>
>>>> Which is strange to say the least, as the per the definition/intent of
>>>> generics, the code in mya should not know anything about the types that
>>>> will be used when specializing. (in this case complex).
>>>>
>>>> As per the intent of generics the second program above should compile
>>>> just as well.
>>>>
>>>> But then different rules will apply for operators and procedure calls:
>>>> - procedure calls must be resolvable at define time
>>>> - Operators must be resolvable at specialization time.
>>>> No principal problem (we can define it so), but strange at least.
>>>>
>>>
>>> It is correct that the second doesn't compile. To make the second
>>> compile, the overloaded operators for the complex type must be defined
>>> inside complex (which was/is? not possible).
>>
>>
>> 1. The + is not defined 'inside' integer either. Why should it be
>> required for a record ?
>
> Internal types are special.
>
>>     What kind of strange reasoning is that ?  Are we going to redesign
>> operators for records ?
>
> For pascal like generics it might be necessary to rethink some design
> considerations, yes.
>
>>     (I suspect this is why it is possible to add type restrictions in the
>> Delphi/.Net implementations)
>>
>> 2. If I have my own overloaded version of '+' for a record, the above
>> means that it
>>     cannot ever be used for generics, while it will be used for all my
>> other code.
>>
>> Say I define a type, and decide not to put the operators inside the record,
>> for whatever reason. I am happily unaware of generics. Along comes an
>> afficiniado of generics, and wants to use my type in generics, but hits
>> the above problem. He is stuck.
>
> No. He can define a record helper operator. The question is simple: do
> we want generics behave like macros or more like .Net generics. Some
> hybrid approach is imo wrong.

Oh dear... I have completely forgotton about operators in record helpers 
in my implementation...

Nevertheless I don't think this would help in the current situation. 
Let's assume he uses a 3rd party record that does not contain operators 
(only global ones) and he uses a 3rd party generic type. Let's further 
assume that the user can't or does not want to modify those two types. 
Then he can't use a record helper during the specialization, because 
that helper isn't available in that time like the global operators 
defined along side the record aren't.

I must admit though that I have a really bad feeling about my above 
assumption when I think about my lookup code... so when I enable 
operators in record helpers it might even work currently by accident O.o

Regards,
Sven