On Fri, Aug 19, 2011 at 9:45 PM, Gordon Woodhull <gordon@woodhull.com>wrote:
Hi All,
The review of Vicente Botet Escriba's Conversion library starts today and ends August 29.
[...]
* What is your evaluation of the design?
Overall, I think it is designed well for its stated goal.
* What is your evaluation of the implementation?
I didn't look.
* What is your evaluation of the documentation?
Good.
* What is your evaluation of the potential usefulness of the library?
Here is where I'm getting tripped up; I will expound below.
* Did you try to use the library? With what compiler? Did you have any problems?
No.
* How much effort did you put into your evaluation? A glance? A quick reading? In-depth study?
I've been keeping up with other's review comments, and engaged myself a little bit.
* Are you knowledgeable about the problem domain?
I think so...?
And finally, every review should answer this question:
* Do you think the library should be accepted as a Boost library? Be sure to say this explicitly so that your other comments don't obscure your overall opinion.
To be honest, I'm very ambivalent. I'm hoping we can come to a consensus on whether this library is appropriate for Boost or not. Of course, "informal reviews" and discussion are also welcome.
Let me first say that the primary reason for deciding against outright acceptance at the moment is purely philosophical and may be entirely misguided. It seems to me that Conversion offers a generic solution to a problem that rarely (if ever?) arises in generic contexts. This makes me question its utility. Vicente, I would love to see an example where Conversion solves a real conversion-between-unrelated-types problem (that couldn't be solved in an equally simple or simpler way) within a generic context; it's just difficult for me to imagine this, which might be entirely my own mental block problem. I think my perspective has been colored by my own experience in trying to solve this problem. I, too, needed a framework within which to convert unrelated (numeric) types, and built a framework similar (but, of course, simpler) to what Conversion offers. Upon reevaluation, though, I concluded that this framework was too inflexible and a visitor-based solution would be more appropriate *for my application*. For me, I needed additional *context* to convert between certain types, and I also wanted to support the flexibility of different conversion *implementations*. In applications requiring conversions between unrelated types, context and varying implementations seem to me to be features that would at least occasionally be desired, and there isn't really a convenient way for Conversion to support that. Sure, you can wrap your "from" objects to tag them to select the desired conversion implementation or to bundle them with the desired context, but I wouldn't consider that very convenient and it certainly reduces genericity (much better to have the implementation and context dictated by the functor). Aside from my philosophical objections, Conversion has the potential to promote ODR violations, and this just seems like a Bad Thing. Sure, there are other extendable operations (e.g., operator< or operator==) that could cause ODR violations if defined for unrelated types by some 3rd party, but Conversion seems unique in the sense that it provides an extension point for an operation that *inherently* must operate with two unrelated types, with the typical case that this operation is defined by some 3rd party disassociated from the involved types. I don't think education is sufficient to adequately mitigate this problem. But I don't know, maybe I'm taking a corner-case problem and blowing it up into a big issue... I apologize for not really discussing this earlier in the review, but I did allude to it earlier in the week and I've really just been spending a lot of time thinking if the above issues are real problems or not. I can't convince myself that they aren't yet :/ I'll try to give specific comments related to the documentation and interface sometime later, in case it is decided that Conversion should be accepted. - Jeff