Re: Regex refactoring

[Jonathan Wakely <jwakely dot gcc at gmail dot com>]

On 7 November 2013 18:15, Tim Shen wrote:
> On Thu, Nov 7, 2013 at 11:49 AM, Jonathan Wakely <jwakely.gcc@gmail.com> wrote:
>> The most common instantiations of _Compiler will probably use const
>> char*, std::string::iterator and std::string::const_iterator. It would
>> be good if they could all share code, since they all operate on the
>> same underlying character type, but I don't know if that's possible.
>
> We may read whole input characters into a basic_string<_CharT> then
> use it to initialize _Compiler. Now it can be simplified to:
>
> template<typename _TraitsT>
>   class _Compiler
>   {
>     typedef typename _TraitsT::char_type _CharT;
>     ...
>     _Compiler(basic_string<_CharT>&& __input_string);
>   };
>
> It requires more memory, but I don't think storing a string which
> describing a regex is unacceptable.

I've already added this generator function to compile a regex, to
simplify using __detail::_Compiler

  template<typename _FwdIter, typename _TraitsT>
    inline std::shared_ptr<_NFA<_TraitsT>>
    __compile_nfa(_FwdIter __first, _FwdIter __last, const _TraitsT& __traits,
          regex_constants::syntax_option_type __flags)
    {
      using _Cmplr = _Compiler<_FwdIter, _TraitsT>;
      return _Cmplr(__first, __last, __traits, __flags)._M_get_nfa();
    }

So I can overload it for std::basic_string<C, T, A> and std::vector<C,
A> iterators to dispatch to the specialization for _Compiler<const
C*>.

That will use the same compiler for most contiguous ranges of type C,
without allocating any memory.