[boost] Re: Formal review of "Output Formatters" library begins today

From: Vladimir Prus (ghost_at_[hidden])
Date: 2004-09-14 03:54:16

Roland Richter wrote:

> Reece and fellow boosters,
> 
>   I have a special interest in Output Formatters working together
>   with lexical_cast. The idea is this:
> 
>   Since lexical_cast internally uses a stringstream and its
>   associated operators >> and <<, and since outfmt defines
>   << and >> for STL containers, it should be possible to
>   lexical_cast any STL container.
...
>   the reverse "input" operation
> 
>     boost::lexical_cast< std::vector<int> >( "[ 7, 9 ]" );
>     // throws bad_lexical_cast
> 
>   fails. This is because lexical_stream turns off white space skipping,
>   and outfmt uses "[ ", ", ", and " ]" (with all those nifty spaces)
>   as default formatting.
> 
>   The problem is that I can't pass any formatting options to
>   lexical_stream at runtime. Hence, I'd like to propose that
> 
>   a) either the default formatting of containers is changed to
>      "[", ",", and "]",
>   b) or a compile-time mechanism (macro? template magic?) should
>      be provided to set the formatting.

I've made a noise about this in the past. I strongly believe that current
lexical_cast behaviour does not play nice with existing stream operators
(which are commonly written to assume whitespace is skipped). There's no
good reason for that, and lexical_cast should not use the "noskipws" flag.

- Volodya