[fpc-pascal] FPImage and GetDataLineStart

Michael Van Canneyt michael at freepascal.org
Fri Apr 22 19:05:30 CEST 2011

On Fri, 22 Apr 2011, Florian Klämpfl wrote:

> Am 22.04.2011 14:01, schrieb michael.vancanneyt at wisa.be:
>> By this rule, the helper class/operator/beast you proposed in the other
>> mail
>> should also not be available, because it is not known during definition.
>> Just as a helper is 'attached' to a type, an operator is equally
>> 'attached' to the type. Both can be "attached"  by a third party that
>> requires it : all that is needed to use it is that it is in your current
>> scope.
> IMO a helper is bound closer to a type than an operator.

Please explain ?  To my understanding, they're on exactly the same level ?
(from a language feature point of view).

I mean, what can be more close to a type than a := operator ?

>> To me this means that if you allow the one, you should - logically -
>> allow the other.
>> (or vice versa)
> With the same reasoning, one should allow also functions taking the type
> as parameter.

Functions are different, because they are not something you attach to a type.
A function just happens to have one parameter (out of possibly many) of a 
particular type.

A class helper and operator are explicitly designed for this type, enhancing it
to be able to work with it.

But that's beside the point:

I just think that if you except one and the other not, then that does not 
look like a very consequent application of generics, more like patchwork 
instead of a well integrated language feature.

I see no reason why you would prefer one language feature above another 
in such cases.


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