Re: [boost] Re: Re: [filesystem] Major changes before standardization

From: Peter Dimov (pdimov_at_[hidden])
Date: 2004-11-18 08:18:29

Vladimir Prus wrote:
> Peter Dimov wrote:
>
>>> The very same question arises with path/wpath:
>>>
>>>   path p( "foo")
>>>   p /= wpath(L"bar");
>>
>> We can avoid it by not defining a mixed operator/=, though.
>
> Yes, but what if I need to do this? Then there should be some
> conversion function, and why that conversion function can't be called
> by mixed operator/=, then?

Because the library may not convert the way you want it to. Even if a wpath 
is convertible to a path, the converting constructor should probably be 
explicit.

    p /= wpath(L"bar");

seems fine at first sight, but it's actually an error; it should have been

    p /= "bar";

Without an implicit conversion,

    p /= path(wpath(L"bar"));

the redundant conversions are much more evident.

And to get back to the original question, p always stores a narrow path, so 
there is no ambiguity whether L"bar" needs to be narrowed, or "foo" is to be 
widened. There is a potential ambiguity with a mixed operator/, though, if 
one is provided. Which is why there shouldn't be a mixed operator/. ;-)