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Subject: Re: [boost] Formal Review Request: Boost.String.Convert
From: Stewart, Robert (Robert.Stewart_at_[hidden])
Date: 2009-02-18 08:52:35

On Tuesday, February 17, 2009 5:43 PM
Emil Dotchevski wrote:
> On Tue, Feb 17, 2009 at 2:34 PM, Steven Watanabe
> <watanabesj_at_[hidden]> wrote:
> > Emil Dotchevski wrote:
> >>
> >> The two approaches are:
> >>
> >> 1) Define a "to_string" interface and a separate, independent
> >> "from_string" interface
> >>
> >> 2) Define a single interface that can go to and from string
> >>
> >> The second approach introduces coupling between to_string and
> >> from_string. This coupling must be justified, you need to get
> >> something in return. The only "something" I see here is
> that it lets
> >> you write code which doesn't "know" if it's going "to" or "from"
> >> string.

The coupling is not of implementation but of interface. They are opposite sides of a single coin, so coupling them is not a terrible thing.

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.

> > The only other benefit, is possible syntactic nicity. Note that
> > this function can be in a very light weight header that forwards
> > to the correct implementation, so the coupling would be minimal.
> Your description is identical to 1) as far as I'm concerned because
> there is no coupling between to_string and from_string (the coupling
> is between convert() and to_string/from_string). However, in this

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

> design it makes sense convert() to be a separate library altogether,
> assuming it's scope goes beyond string conversions alone.

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.

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

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