[fpc-devel] Re: enumerators
DrDiettrich1 at aol.com
Wed Nov 17 01:27:20 CET 2010
Marco van de Voort schrieb:
> In our previous episode, Hans-Peter Diettrich said:
>>> Yes, but the realisation should be that the holding on array indexing is
>>> what makes it expensive. The problem could be strongly reduced by removing
>>> such array indexing skeleton from all routines where it is not necessary.
>> Why fall from one extreme into the other one?
> I don't consider it an extreme, on the contrary. Trying to fix this is
> extreme IMHO.
Sorry, I understood that you want to replace all for loops by iterated
>>>> UTF encodings have their primary use in data storage and exchange with
>>>> external API's.
>>> And in memory.
>> That's the design flaw, IMO. When UTF-8 strings are re-encoded before
> How, when? How do you avoid repeated encoding/decoding/encoding cycles?
The encoding is only changed on demand. Once converted into a
computational format (e.g. UCS2), the internal representation deserves
no more changes. Another conversion may occur when a copy in a different
encoding is requested; since a copy operation already is O(n), a
conversion will not increase that order.
The result were a general Unicode string class, not bound to a specific
encoding, similar to the Delphi Unicode string representation.
> I don't see why a string should be a class. In FPC it is already a first
> class type.
Name it as you like, but a first class string type is only a container,
that can contain data of any kind - every data type or structure can be
seen as a collection of bytes or chars.
Take Unicode, zip or graphics encodings as examples for data types, that
can be stored in such a container, and you'll see that every different
encoding deserves different support functions - the data type becomes
polymorphic. Having reached that point I see a need for a base class,
that reflects the *nature* of the information, from which classes for
specific encodings can be derived. A user will be happy with the
abstract type (see TStrings), and must not bother with specific
encodings, that can result in bad behaviour when not choosen properly.
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