2011/8/28 Vicente J. Botet Escriba <vicente.botet@wanadoo.fr>:
Le 28/08/11 09:43, Antony Polukhin a écrit :
* What is your evaluation of the design?
It is simple and looks good. But consider the following situation: lexical_cast<char>(1) and numeric_cast<char>(1) will produce output. It must be documented, which cast will your library use in which cases.
The documentation of header <boost/conversion/std/string.hpp> includes "Include this file when using conversions from/to |std::string| via |lexical_cast|. "
And that`s were the problems begin! If user included this header, all his conversion will convert convert_to<char>(1) as lexical cast does? And what if the user whants conversions, like numeric cast does? More examples: Two developers are working on different parts of project. Developer #1 uses convert_to<char>(1) in his code and wants behavior like numeric_cast. He also uses some headers, which is maintained by Developer #2. At one day Developer #2 includes <boost/conversion/std/string.hpp> in one of his headers. And we get really hard detectable errors!
There must be some tags, to allow user to choose, which conversion is required. There are some dummy::type_tag tags in source code, but looks like they are not used, and not documented!
They are used to overload the conversion functions. The class is documented here https://svn.boost.org/svn/boost/sandbox/conversion/libs/conversion_ext/doc/h.... This https://svn.boost.org/svn/boost/sandbox/conversion/libs/conversion_ext/doc/h... tutorial section explains how to use it.
I could not determinate, for what are this tags used from the documentation. Can we use them, to call numeric_cast instead of lexical_cast? Can we use them, to call Boost.Coerce instead of lexical_cast? can we use them, to support some parameters for Boost.Coerce?
Could you elaborate on how you see the library can use these tags?
Some thing like this: convert_to<char>(1, numeric_tag); convert_to<char>(1, coerence_base<16>); convert_to<pair<char, char> >(make_pair(1,1), lexical_tag); convert_to<double>(1); // We can also convert without tags Best regards, Antony Polukhin