[fpc-pascal] FPImage and GetDataLineStart

Florian Klämpfl florian at freepascal.org
Fri Apr 22 12:18:16 CEST 2011

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.

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