[fpc-pascal] FPImage and GetDataLineStart

michael.vancanneyt at wisa.be michael.vancanneyt at wisa.be
Fri Apr 22 12:06:31 CEST 2011

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 ?
    What kind of strange reasoning is that ?  Are we going to redesign operators for records ?
    (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.


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