Re: [boost] Preliminary submission: Boost.Proto DSEL Framework

From: Eric Niebler (eric_at_[hidden])
Date: 2007-04-04 14:20:47

Larry Evans wrote:
>    On page:
> 
> http://boost-sandbox.sourceforge.net/libs/proto/doc/html/boost_proto/user_s_guide/quick_start.html
> 
>    the sentence:
> 
>      Notice that in order to build a Proto expression template, at least
>      one argument in the expression must be a Proto-ified. In this case,
>      that is done with the terminal<> class template, which is used to
>      wrap std::cout.
> 
>    was, at first, unclear to me because evaluate just had one argument;
>    however, "one argument in expression" suggests there could be more
>    than one.
> 
>    The following would be clearer to me:
> 
>      Notice that in order to build a Proto expression template, at least
>      one subexpression of the whole expression must be a Proto-ified. In
>      the case of:
> 
>        cout_ << "hello" << ',' << " world"
> 
>      this one Proto-ified subexpression is cout_, which is the
>      Proto-ification of std::cout via wrapping by the terminal<> class
>      template.
> 
>    I hope that's right.  If not, then I still don't know what the
>    sentence means :(

Yeesh, I was being very imprecise. Your's is an improvement, but it's 
still not completely accurate. It needs to say that for any /operator/ 
in an expression, at least one operand must be proto-ified. Otherwise, 
proto's operator overloads will not be found.

-- 
Eric Niebler
Boost Consulting
www.boost-consulting.com