On 5/24/2020 12:38 PM, Joaquin M López Muñoz via Boost wrote:
El 24/05/2020 a las 14:52, Edward Diener via Boost escribió:
On 5/24/2020 4:20 AM, Joaquin M López Muñoz via Boost wrote:
El 23/05/2020 a las 22:46, Edward Diener via Boost escribió:
I am totally against the idea that some code which works perfectly in C++03, as well as all other C++ standard levels, needs to be unnecessarily updated to some later C++ standard level in order to be acceptable to anyone.
This looks somewhat at odds with one of the stated goals of your cxx_dual lib:
"On a more practical basis the CXXD library is for:
1. Programmers writing code not using C++11 syntax who still want to target some C++11 libraries if the code is compiled in C++11 mode. [...]"
I do not see why you think the statement above is at odds with what I previously asserted. Whatever might have been added to a Boost library which became a C++ standard library in C+11 or beyond could hardly have been done just to add unnecessary features. I am not against a library being updated to use features of a later C++ standard when those updates are predicated on improving a library in specific ways that make it worthwhile to add such features.
I'm not sure I'm parsing your sentences right, but does that mean you're ok with a library using cxx_dual from scracth but not ok if a Boost-reliant lib is later updated via cxx_dual *only* to reduce Boost dependencies in C++11?
No. I am ok with a library changing itself to use C++ standard libraries instead of their Boost equivalents in any way it wants, whether using cxx-dual, whether creating its own interfaces for both Boost and the C++ standard equivalent, or whether just switching from using Boost to the C++ standard equivalent. But I am aware that such a change takes work, and will displease some end-users. If the Epoch proposal is merely to get a given Boost library to create another version of itself where it uses C++ standard libraries instead of Boost libraries so it can be part of a later Epoch I can see the value of your proposal, but again who will do the work of this transformation ? But if the Epoch proposal entails forcing a given library to use some features of a C++ standard so that it can be part of an Epoch, I see that is a failure of conception. If we are just talking about library dependencies, then a Boost library which has 0 or more dependencies on only C++ standard libraries of a given Epoch belonging to that Epoch is actually fine with me. But this of course means that a Boost library which has no dependencies on either Boost libraries or their C++ standard equivalent libraries of a given Epoch belongs to all Epochs, which is the way it should be IMO. So Boost PP, as an example, belongs to all Epochs.
The gist of your proposal which seems to me to be highly flawed is the idea that at a certain Epoch level all dependencies of a library must also exist at that same Epoch level or higher. How realistic is such a goal ? If library X at Epoch level nnn successfully uses library Y at Epoch level nnn-1, why should library Y be arbitrarily updated [...]
I understand you meant "should library X be arbitrarily updated" here.
No, I meant that library Y should not be arbitrarily updated so that library X can be considered valid for Epoch nnn. The only case I see where library Y would need to be updated, with perhaps another version at Epoch level nnn, would be if library Y had a dependency on a Boost library where an equivalent C++ standard library which works at Epoch level nnn was available.
[...]for no good practical reason to use C++ features of Epoch level nnn ?
The reason is to reduce internal Boost dependencies.
Adding C++ features at a certain C++ level rarely has to do with dependencies as opposed to the necessities of programming design. If adding a feature at a certain C++ level was able to reduce a dependency of a library to another library I would in general be all for it. But just let's take a library that is designed in such a way that it does not need any features of, let's say, C++11. Why would anybody want to add some feature just for the sake of saying that the library is at Epoch 11, when such a feature is unnecessary in the design of the library. This is what I mean by "absurdity".
I am pretty sure you can see the absurdity of such a determination as that.
I admire your confidence but not your perspicacity, as I indeed see no absurdity here.
Take for instance Boost.Beast, which depends on boost::string_view but can be made to depend on std::string_view instead via BOOST_BEAST_USE_STD_STRING_VIEW. Shall I take that you deem this ability absurd?
Not at all. But take a library which works fine at the C++03 on up level, such as TTI, and has no dependencies on other Boost libraries which can be dropped by adding some arbitrary feature of C++ 11 on up. Why should not this library be used by an Epoch library at the C++11 level if its usefulness is apparent to that Epoch library. And why disqualify that Epoch library from its level just because TTI does not use C++11 features. The gist of our disagreement is that I can see the usefulness of your proposal regarding Boost dependencies versus C++ standard equivalents, but not regarding the arbitrary distinction of whether some library uses some C++ feature of some C++ standard level. I would agree wholeheartedly with the idea that for any given Boost library, X, at no matter what C++ standard level, which uses 1 or more other Boost libraries when a C++ standard equivalent is available at some C++ standard level, that it would be advantageous for end-users to have another version of that library which uses the C++ standard equivalents. But doing such work is hardly trivial.