[fpc-pascal] Ideas for namespace implementation
Hi, As I stated in another thread, namespaces are not perfect, but they do work, and they do greatly reduce the chances for unitname or classname conflicts. Other languages and frameworks (Java, .NET, C++ etc) already showed this. How visible is the unit name conflict problem? Just think, how many projects are there that use the unit names (or would like to use these common names): constants.pas utils.pas etc... Extremely common names, and are really good names for what they contain, so why can't we use them in our projects? Namespaces will resolve this problem. What we need to discuss, is how to implement namespace support in FPC. Some ideas I can think of... please list your own if you have some: 1) Follow the "dotted" notation for unit names as implemented in Delphi. Cons: - They force rather long unit names, which is frowned upon in the Pascal community (for whatever reason). Ambiguities couldn't appear, but they are rather easy to overcome with a simple language rule. Object Pascal already have many language rules, this will just be a new one. See the following Mantis report for details: http://bugs.freepascal.org/view.php?id=14439 2) Another idea is in a way similar to how compiler defines work. This idea tries to resolve the problem in (1) with long unit names and with least amount of resistance to existing code. A namespace can be applied to a single unit, or to a group of units (think of it as a "package"). To get this to work, we will have to introduce a new keyword and a new compiler parameter. Here follows examples of both. // per unit unit utils namespace companyxyz; uses ... end. ... or applied at compile time to all units being compiled. // our sample unit - as normal, nothing new unit utils; uses ... end. $ fpc -namespace=companyxyz utils.pas constants.pas ... ... if a conflict occurs, then you reference the unit with the full namespace. eg: uses companyxyz.utils; // because unit names must be valid identifier and thus, // can't contain dots, when the compiler sees this, it knows // companyxyz. is a namespace reference. Pros: - No long unit names are required. - We can use all the easy unit names for projects. eg: utils.pas, constans.pas etc. - Can be applied to existing code without any code changes, simply by adding a new namespace compiler parameter when compiling that existing code. Thus, FPC's RTL and FCL, or fpGUI or Lazarus etc could apply it too, to their makefiles. - referencing via a namespace is only needed when a conflict occurs, other than that, units are used as normal. - If no namespace is specified, then it automatically falls under the "global" namespace - maybe using the namespace value "global" and will be similar to all units containing the following: eg: unit myunit namespace global; ... end. ... or being compiled with 'fpc -namespace=global ' 3) Automatically add the directory where the unit is located, as the namespace. Similar to what Java does. I'm sure given more time, I could come up with some more ideas, but I rather like (2) because it could be applied to all existing code, without any code changes required. -- Regards, - Graeme - ___ fpGUI - a cross-platform Free Pascal GUI toolkit http://opensoft.homeip.net/fpgui/ ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-pascal
[fpc-pascal] Re: Ideas for namespace implementation
On 25 July 2010 19:16, Michael Van Canneyt wrote:
>
> What unit name conflicts ? In 15 years that I work with Delphi and FPC, and
> I have use many many packages, I encountered exactly 1 conflict:
Then you are extremely lucky. I have experience stacks of unit name
conflicts in my years of programming. Have you never had the urge to
use the unit name: constants.pas? utils.pas?
> the strutils of rxlib, which conflicted with strutils introduced in a later
> version of Delphi. The RX copy was renamed to rxstrutils, and that was it.
A perfect example of the problem!
* Compilers get preference over the easy and well descibed unit
names, while other projects must now rename there units.
* Other projects now have to live with crappy named units with ugly prefixes.
* can't use underscores because for some reason it is frowned appon,
so now you
get odd looking units where the prefix ends with the same letter
as the original unit names.
Utilities functions that work on Strings - wouldn't it make sense to
have them in a unit: strutils.pas?
Currently we can't, even though the unit name perfectly describes the
function of that unit - so we have to shun from the ideal name. If we
don't, we are guaranteed to get conflicts in our projects. So now only
the "compiler" projects like Delphi or FPC my use such names - that is
crap.
> I am sorry, but I think that the seriousness of the problem is very much
> overestimated. Wanting to type rx.strutils versus rxstrutils. Really ?
And my suggestion (2) will reduce such syntax *only* when a conflict
has occured, without long unit names.
> And let us not forget: most component vendors must support older versions of
> Delphi, so they are barred from using the dotted unit name syntax anyway.
Which option (2) I suggested will also handle via a namespace compiler
parameter or the 'namespace ' in the unit, but declared inside
a IFDEF checking for compiler version: eg
unit utils {$IFDEF Ver2_4_x} namespace myproject {$ENDIF};
uses
...
end.
--
Regards,
- Graeme -
___
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http://opensoft.homeip.net/fpgui/
___
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Re: [fpc-pascal] Re: Ideas for namespace implementation
On Sun, 25 Jul 2010, Graeme Geldenhuys wrote: On 25 July 2010 19:16, Michael Van Canneyt wrote: What unit name conflicts ? In 15 years that I work with Delphi and FPC, and I have use many many packages, I encountered exactly 1 conflict: Then you are extremely lucky. I have experience stacks of unit name conflicts in my years of programming. Have you never had the urge to use the unit name: constants.pas? utils.pas? No. Because I don't see the difference between having to type uses wisa.utils; versus uses wisautils; The latter is even shorter. So I really don't see the gain. The discussion is not about namespaces. Object Pascal HAS namespaces, namely units. The discussion is about 'enhancing' the namespace to allow one or more dots in the name. That said, I don't really care whether the . ends up in the compiler or not, but I do think it is much ado about nothing. Yes, it may be nice to have, but no, it is not urgent and not the end of the world if we don't do it. Unicode strings is orders of magnitude more important. Michael. ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] Re: Ideas for namespace implementation
On 25 July 2010 23:30, Michael Van Canneyt wrote: > > The discussion is not about namespaces. Object Pascal HAS namespaces, > namely units. The discussion is about 'enhancing' the namespace to allow one > or more dots in the name. With the importance that the '.' is only needed when resolving a conflict - all other instances, you will just use the unit name as normal. Also, the '.' usage is only limited to the uses clause. At least we will be able to easily use more logical unit names without the fear of getting unit name conflicts. > Unicode strings is orders of magnitude more important. I wasn't arguing what is/isn't more important that other tasks. I'm gathering information and feedback on a feature request to enhance namespace support to reduce unit name conflicts. Just because Unicode strings haven't been implemented yet, doesn't mean we maybe implement something else. Regarding the cpstrnew branch: I'll try and resolve my Unicode String branch (cpstrnew) compilation issues this coming week (or at least report the issue with more details). Since the resync with Trunc, I can't compile that branch, and thus can't submit my local changes I have so far. -- Regards, - Graeme - ___ fpGUI - a cross-platform Free Pascal GUI toolkit http://opensoft.homeip.net/fpgui/ ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-pascal
