The great compromise of the D standard library

[Reiner Pope]

Bill Baxter wrote:
> Bruce Adams wrote:
>> Bill Baxter Wrote:
>>
>>> Darryl B wrote:
>>>> == Quote from Ender KaShae (astrothayne at gmail.com)'s article
>>>>> I have great misgivings over the divide among the D community 
>>>>> between standard
>>>> libriraries.  The contintion will no doubt eventually lead to a  
>>>> schism reduce the
>>>> reusibility of D code.
>>>>
>>>> I absolutely agree with this point. One of the first eyebrow-raising 
>>>> experiences
>>>> for me, moving to D, was learning of this 'alternate' standard 
>>>> library. The 'D'
>>>> standard library should be 'the' D standard library, shouldn't it? 
>>>> You may as well
>>>> be writing in a different language, going from one lib to the other. 
>>>> You really
>>>> have to specify which 'flavor' of D you use when speaking to others, 
>>>> and a Tango
>>>> dev may not even want to look at a problem someone has if they were 
>>>> using Phobos.
>>>> The separation of the 'D-Tango' and 'D-Phobos' factions is 
>>>> detrimental to the D
>>>> language as a whole, IMO.
>>> There's also D2.0 which is a completely different, incompatible 
>>> version of D.  So really there are *three* different incompatible 
>>> versions of D to choose from right now (yes you can get some source 
>>> code to compile with both D1 and D2, just like you can get some code 
>>> to compile with either Tango or Phobos).
>>>
>>> I was all for adding of const to D, but my vision was for it to get 
>>> added relatively quickly and become the one-and-only D.  Add it 
>>> quickly, get everyone to fix their code, and then forget there ever 
>>> was a D without const.  Leave it in the dust.  Just like we forgot 
>>> about D with regular expression literals, or D with the === operator.
>>>
>>> But instead we got a D-without-const codified as a permanent, 
>>> unchanging standard and D-with-const as a new, incompatible, 
>>> competing standard.
>>>
>>> Taking a step back it just seems really silly for a niche language 
>>> like D to have so many factions.
>>>
>>> So here's a little proposal to maybe help mend the D1/D2 schism a 
>>> bit: add -v2 compatiblity switch to D1 that would cause it to just 
>>> ignore D2's const and invariant declarations.  That would make 
>>> writing code that works on both a lot easier.
>>>
>>> After porting a bit of D2's std.* to D1, it seems that the main 
>>> issues are just const(foo)[] and invariant(foo)[] constructs here and 
>>> there. The fix is almost always just to remove them.  So if the D1 
>>> compiler could be made to ignore those then that would remove most of 
>>> the hassle of making code compatible between D1 and D2.
>>>
>>> --bb
>>
>> Is this really worth the hassle? If you check Walter's recent postings 
>> sorting out const is on the list for the next release.  He know's it 
>> sucks, he started a thread on it remember. I don't think we have long 
>> to wait for the next try. He could get it wrong again but given all 
>> the feedback and some time to think maybe he's got it right this time 
>> (or at least right enough).
> 
> D1.0 is still intended as a long-term support, stable version of D.  So 
> D1.0 is not going away for a while even if const turns into everybody's 
> favorite feature of D2.0.  And even if the new const design has 
> everybody doing backflips of joy, code written using it it will still be 
> incompatible with D1.0, and making it compatible will still be a pain 
> since D lacks the equivalent of something like
>    #define invariant /*nothing*/
> 
> --bb

For what it's worth, something like this should probably work

template Const(T)
{
     version (D1)
         mixin("alias const(T) Const;");
     else
         mixin("alias T Const;");
}

    -- Reiner