Phobos/Tango Unification Plans

[Sean Kelly]

Bruno Medeiros wrote:
> Don wrote:
>> Benji Smith wrote:
>>> I was just looking through bearophile's library (which is based on 
>>> Phobos) and thinking about how it's too bad that I can't use it 
>>> because my code is all based on Tango.
>>>
>>> I know there are plans currently in the works to implement a 
>>> compatible runtime layer, via Sean's druntime project. And it'll be a 
>>> breath of fresh air to get rid of the basic incompatibilities in the 
>>> two runtimes.
>>>
>>> But if that's all that happens, it'll still leave an undesirable 
>>> situation, since all the other userland stuff will be incompatible.
>>>
>>> Eventually, any significantly complex project is likely to have some 
>>> dependent libraries built on top of both Phobos and Tango. At the 
>>> very least, string-processing routines from both libraries will get 
>>> compiled into the final executable.
>>>
>>> Not only will that result in duplication of functionality (and code 
>>> bloat), but it'll also mean a bunch of bit-twiddling whenever sending 
>>> a Tango type into a Phobos-dependent library function (and vice versa).
>>>
>>> Are there any plans in the works to mitigate that problem? Like, 
>>> perhaps, negotiating a common API so that at least the names and 
>>> argument types are the same in both libraries?
>>>
>>> I'm sure the two libraries will always include different subsets of 
>>> functionality, but whenever they implement the same basic features, 
>>> it'd be great if they used a compatible API.
>>>
>>> --benji
>>
>>
>> That could have some difficult aspects, but here's an uncomplicated 
>> second step: The math libraries for Tango and Phobos aren't merely 
>> compatible, they are THE SAME! They are a cut-and-paste of each other, 
>> with a couple of trivial name changes.
>> There are no licensing issues or personality clashes to worry about -- 
>> I've written most of both of them. They have no dependencies on 
>> anything else in either Phobos or Tango. I have write access to 
>> repositories of both Phobos and Tango.
>> YET -- there are two bodies of code! This is absolutely ridiculous, 
>> and it's driving me mad.
>>
>> How can we turn this into ONE body of code?
>> It will only be possible if there is a namespace which is present in 
>> both Tango and Phobos. There are exactly three ways in which this can 
>> be done:
>> Either
>> (1) Tango needs to include part of the std namespace,
>> (2) Phobos needs to include part of the tango namespace, or
>> (3) Both need to start including a new namespace which is common to both.
>>
>> Of these options, I think (2) is the least natural. For (1) to work, 
>> the modules invoved would need to be clearly designated as common.
> 
> I don't get it. Why is it that "For (1) to work, the modules invoved 
> would need to be clearly designated as common." ? Since Tango will 
> become compatible with Phobos (same runtime), can't Tango just 
> use/depend-on some of Phobos functionality?

I believe Tango aims to continue being separately distributable from 
Phobos, so this isn't likely to happen.  Another option would be for the 
math package to live in a separate project that's bundled with both 
libraries, though I don't know how either team feels about the logistics 
of such an arrangement.


Sean