[boost] Wave and flex_string [was: Re: Wave C++ Review Begins Today...]

From: Reece Dunn (msclrhd_at_[hidden])
Date: 2005-02-11 10:39:08

Hartmut Kaiser wrote:
> Pavel Vozenilek wrote:
> 
>>I think Wave should become part of Boost.

I agree. It is an invaluable tool. This would especially be the case if:
1.  There is a wave.jam toolset for BBv2.
2.  It is easy to chain wave in the build process. That is:

exe demo : main.cpp ; # compiler preprocessor
exe demo : main.cpp : <preprocessor>wave ; # wave preprocessor

>>1. Some parts may be separated:
>>
>>- flex_string may be standalone library
>>
>>  (flex_string.hpp: the link to CUJ HTML page should be
>>   replaced to link to Andrei's website, CUJ is accessible
>>   to subscribers only).
> 
> This was discussed already on this list in conjunction with the dicussion
> about the const_string library. I don't know, what's the current status, but
> IIRC there were some people interested in putting together several different
> string implementations compatible with std::string et.el.

I have been working on this using a variant of flex_string for my 
fixed_string class because flex_string does not handle the way I am 
implementing flex_string.

One issue I have with flex_string is that it is too big. Granted, that 
is because the std::string definition is big as well. Given this, I have 
been factoring out the various methods into groups (iterator, element 
access, etc.)

The new approach makes use of the CRTP technique, with the helper macro:

#define BOOST_CRTP_IMPL(T)\
          T & derived(){ return *static_cast<T *>(this); }\
    const T & derived() const{ return *static_cast<const T *>(this); }

This is more in line with the approach for iterators and can be expanded 
to include common patterns for container implementations (e.g. with 
iterators/reverse iterators).

This would make it easier to use subsets of the std::string interface. 
For example, Maxim's const_string doesn't use the mutating methods.

I have also made several modifications to Andrei's flex_string: using 
Boost's reverse_iterator (for msvc-6.0 support) and the strings 
char_traits for copy/move/etc. vs using the pod_* methods.

Regards,
Reece