Phobos 2

[Mike B Johnson via Digitalmars-d]

On Thursday, 1 June 2017 at 20:58:52 UTC, H. S. Teoh wrote:
> On Thu, Jun 01, 2017 at 06:40:05PM +0000, Brad Anderson via 
> Digitalmars-d wrote:
>> A (surely controversial) idea popped into my head while 
>> talking in #d on Freenode. The C++ guys are making an STL2 
>> (the highlight of it being that it is range based). What about 
>> taking all the lessons learned from Phobos and creating a 
>> Phobos 2? It wouldn't replace the current version. You could 
>> import either in one program. It also wouldn't be a radical 
>> redesign. Most of Phobos could be used as is. What it would do 
>> is allow fixing some hard or impossible problems without 
>> losing backward compatibility.
>
> +1. I'm for this.  There's just too much code in the existing 
> Phobos that certain (wrong, in hindsight) design decisions are 
> essentially impossible to fix.
>
>
>> We could do away with auto-decoding.
>
> +1000. ;-)
>
>
>> Design it around using Andrei's allocators throughout. Make 
>> the GC optional from the start.
>
> +1.
>
>
>> Fix a few important naming conflicts and discrepancies.
>
> As well as certain less-than-ideal names that we were forced to 
> use because the good names have been taken up by not-so-nice 
> implementations dating from before we had the hindsight to know 
> what the best design was.
>
>
>> There are problems, of course. Rampant code duplication is 
>> probably the biggest (though maybe public imports of identical 
>> code would help a lot).
>> 
>> I don't really expect this to go anywhere but I am curious to 
>> hear what changes you'd all like to see made to Phobos that 
>> can't happen because of backward compatibility.
>
> 1) A big one, not necessarily caused by backward compatibility 
> but more by the sheer amount of code that would need to be 
> fixed / rewritten, is the nasty hairball of a dependency graph 
> among the current Phobos modules.
>
> One particularly egregious example is std.format.  Due to the 
> way it was originally implemented, it depended on a lot of 
> other code (IIRC including std.bigint), so even if all you ever 
> did was writefln("%d"), for example, your program would end up 
> depending on std.bigint, std.complex, and all sorts of other 
> stuff that never actually gets used. This in itself is not 
> necessarily *that* bad, but what really makes it hurt is that 
> many other modules depend on std.format. So you could be 
> importing a seemingly completely-unrelated module, and it would 
> pull in std.format, which in turn pulls in other stuff, and by 
> the end you've basically imported about half of Phobos, with 
> the associated executable bloat, even though you really only 
> needed to call 1 function.
>
> And the icing on the cake is that some of these complicated 
> dependencies are circular, which every now and then cause 
> mysterious linker errors and/or surprising dependence on 
> declaration order, that mysteriously vanish when you move 
> seemingly-unrelated code around.
>
> If we were to go the route of Phobos2, I'd like the principle 
> of pay-as-you-go to be baked into its design from the very 
> beginning. If all you need is to format an int, it shouldn't 
> also pull in std.complex and std.bigint. This can be done by 
> compile-time format strings (which we now have, though it's 
> currently just a frontend to the existing hairball code).  If 
> function X and function Y are essentially independent of each 
> other, they really ought to go into their own (sub)modules, now 
> that we have package.d support in the compiler.
>
> Of course, certain things like std.range.primitives and 
> std.allocator will be depended on by 90% of the other modules, 
> which is unavoidable, but which also means that we need to 
> think VERY carefully about what we put into these foundational 
> modules. If at all possible they should not depend on anything 
> else.
>
>
> 2) A lesser item, perhaps would be to change the definitions of 
> input / forward ranges, so that forward ranges are just 
> by-value ranges, and input ranges are by-reference ranges, 
> instead of forward ranges needing explicit calling of .save to 
> save the iteration state. See:
>
> http://lists.cubik.org/pipermail/digitalmars-d/2015-November/241712.html
>
>
> 3) An even lesser item, but now that we have a chance: clean up 
> the mess
> that is the current isSomeString, isNarrowString, etc.. Well, 
> some of
> them will be useless since we wouldn't have autodecoding, but 
> still, we
> need to sit down and properly design these traits so that they 
> are (1)
> useful, (2) orthogonal, and (3) have sensible names.
>
>
>> Also, how would you approach doing this? An on disk copy of 
>> Phobos with changes would not be an acceptable approach, I 
>> think.
>
> I'd say, start in a different namespace than std, so that the 
> two can coexist until Phobos2 is ready to take over prime time. 
> (And even then, Phobos1 should probably stick around for a 
> while until people have migrated over.)  This new namespace can 
> either be completely outside std, like std2 (bad name, I know), 
> or it can be a dedicated sub-namespace, like std.new.
>
> Preferably it should be something unique and easily greppable, 
> so that when Phobos1 is finally gone, we can replace the std 
> namespace with a simple search-and-replace.  But perhaps it 
> would be best to just choose a new namespace with a nice name 
> instead, like phobos.*, so that std.* will eventually just go 
> the way of the dinosaur.
>
> Once the namespace is sorted out, how we distribute the code 
> should be pretty easy to decide.  It could start off as an 
> independent github repo, perhaps, or a dub package or whatever, 
> then when it becomes mature enough we could graft it into the 
> current Phobos repo, and thereby make it available for all D 
> users, and thus begin the gradual transition from std.*.
>
>
> T

This could be done if a clear plan and layout was created before 
any real work was to start. Phobos should have the look and feel 
of .net IMO(or better, but not worse).


.Net is extremely well organized, logical, and useful.