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Subject: Re: [boost] Formal Review Request: Boost.String.Convert
From: Stewart, Robert (Robert.Stewart_at_[hidden])
Date: 2009-02-18 13:02:07

On Wednesday, February 18, 2009 12:46 PM
Emil Dotchevski wrote:
> On Wed, Feb 18, 2009 at 5:52 AM, Stewart, Robert
> <Robert.Stewart_at_[hidden]> wrote:
> Many times I've needed to_string without needing from_string. In my
> book, this is a strong indication that they shouldn't be coupled.

Your argument isn't compelling. Consider an arbitrary precision integer type. If many times one need only add such values, without also needing subtraction, should those operations be separated one from the other?

> > The directionality you see is due to focusing on string
> with the other things converting to and from strings. If,
> instead, you view it as converting from one thing to another,
> where string can be the source or destination type, then all
> conversions are, effectively, one way.
> Yes, I agree that we can lead the discussion from this point of view.
> In this case we must forget about strings and talk about converting
> between all kinds of different types. You can't just say "it's not

That's what I've been doing almost from the start.

> specifically about strings" and be done with it; we have to consider
> several different use cases in particular, as well as the issue in
> general; how the conversion works, how you configure it, etc. Instead,
> the whole thing even resides in a string namespace. :)

Gee, all of that sounds awfully familiar....

> Because nobody seems to be doing this, I don't see any evidence that

Try again.

> the convert() function we could presumably end up with is any good for
> anything but converting to- and from- strings. And for that use case
> it's inferior to two independent to-string/from-string interfaces.

lexical_cast is used for many type-to-type conversions, not just with strings. Why would this be any different?

> > Indeed, conversion to string is implemented apart from
> conversion from string, but that hardly necessitates total separation.
> What necessitates total separation then?

Separate UDTs. Different domains. Many things.

> > It may well be, as I previously suggested, that there is an
> underlying set of functions for converting to strings and
> from strings to which convert defers. That would permit you
> to get your preferred interface while others could use a more
> generic convert() interface, provided both were documented.
> OK here we agree then. Let's come up with good interface for to-string
> and from-string, and then feel free to propose a separate convert()
> library.

Why is that the necessary approach? Perhaps the end result will be something that satisfies all and there will be no need to document the underlying conversion logic. It's too early.

Rob Stewart robert.stewart_at_[hidden]
Software Engineer, Core Software using std::disclaimer;
Susquehanna International Group, LLP

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