Re: [boost] boost::filesystem request

Subject: Re: [boost] boost::filesystem request
From: Beman Dawes (bdawes_at_[hidden])
Date: 2008-10-30 09:31:29

On Wed, Oct 29, 2008 at 11:33 PM, Edward Diener <eldiener_at_[hidden]>wrote:

> Beman Dawes wrote:
> ...
> The issue for me was just ease of instantiation of a basic_path based
> solely on a string type ( which is actually a character type ). One can not
> currently instantiate a basic_path with:
>
> boost::filesystem::basic_path<std::basic_string<char>,
> boost::filesystem::basic_trait<std::basic_string<char> > > myPath;
>
> where one just specifies the character type.
>
> Why would one want to do that ? For two reasons:
>
> 1) In a VC++ program which may be multibyte or Unicode depending on a
> compiler option, we would have:
>
> boost::filesystem::basic_path<std::basic_string<_TCHAR>,
> boost::filesystem::basic_trait<std::basic_string<_TCHAR> > > myPath;
>
> 2) A template class or template function taking a character type parameter
> would just pass that type in to filesystem to instantiate the correct type
> path.
>
> So I do not know whether your version 3 solves makes that easier or not,
> but hopefully it does.

Here is an example; this code does compile and run correctly under V3:

#include <boost/filesystem/path.hpp>
#include <boost/filesystem/operations.hpp>
#include <string>
#include <cassert>
#include <windows.h>
#include <winnt.h>

namespace fs = boost::filesystem;

typedef std::basic_string<TCHAR> tstring;

void func( const fs::path & p )
{
  assert( fs::exists( p ) );
}

int main()
{
  // get a path that is known to exist
  fs::path cp = fs::current_path();

  // demo: get tstring from the path
  tstring cp_as_tstring = cp.string<tstring>();

  // demo: pass tstring to filesystem function taking path
  assert( fs::exists( cp_as_tstring ) );

  // demo: pass tstring to user function taking path
  func( cp_as_tstring );

  return 0;
}

--Beman