Re: [boost] Re: [filesystem] operator<(path, path)?

From: Victor A. Wagner, Jr. (vawjr_at_[hidden])
Date: 2003-08-23 15:14:32

At Friday 2003-08-22 13:06, you wrote:
>At 11:35 PM 8/21/2003, David Abrahams wrote:
> >Beman Dawes <bdawes_at_[hidden]> writes:
> >
> >> At 06:38 PM 8/21/2003, David Abrahams wrote:
> >>
> >>  >I need to make a mapping over paths.  Is there any important reason
> >>  >there's no operator< provided?
> >>
> >> I don't think it has been discussed. I've had the need myself, but
> >> worked around it by using path::string() to generate the key.
> >>
> >> There were a number of discussions about operator== and !=. They can
> >> be subject to serious abuse and misunderstanding, and so are left
> >> out.
> >
> >Whoa, really?
> >
> >> I'm still not sure if that was the right decision, so might be
> >> willing to review it.
> >
> >I'm curious about it, anyway.
>
>Is path("abc")==path("ABC") true in the sense of being the same path? The 
>correct answer is yes, no, or maybe, depending on the operating system. 
>There are a ton of other examples where two paths which are textually 
>different are sometimes the same path.
>
>The counter argument is that defining path equality as path::string() 
>equality seems natural, even if it doesn't answer the "are they the same 
>path?" question. But this does lead to fragile programs; we can see that 
>in the Boost regression test reporting where slight changes in the way 
>bjam reports paths often break the status tables (which rely on 
>assumptions about path equality.) operator== on paths can be a sign of 
>poor, or at least fragile design.

are we going to suggest to the core committee that   somefloat == 
someotherfloat be removed from the language.  Certainly the fragility on 
path can be no worse.

>--Beman
>
>PS: I just changed the FAQ entry to use that example; it is clearer than 
>the one given before.
>
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Victor A. Wagner Jr.      http://rudbek.com
The five most dangerous words in the English language:
               "There oughta be a law"