[boost] Re: Functions as Filters (was Program Reuse...)

12 Jan 2005

      christopher diggins wrote:
...
----- Original Message -----
From: "Jonathan Turkanis" <technews@kangaroologic.com>
To: <boost@lists.boost.org>
Sent: Tuesday, January 11, 2005 10:56 PM
Subject: [boost] Re: Re: Re: Re: Re: Functions as Filters (was Program
Reuse...)
...
Hi Christopher,
I think I haven't made my main point clear, so let me try to
rephrase it.
Hi Jonathan,
I am pretty sure I understand you. Before I continue, I first want to
know one thing, do you (or anyone else) see any value of being able
to write C++ code like the following?
#include <iostream>
#include <fstream>
#include "fxn_filters.hpp"
using namespace std;
void ToUpper() {
  char c;
  while (cin.get(c)) cout.put(c);
}
I don't see why this is better than

   struct toupper_filter : input_filter {
        template<typename Source>
        int get(Source& src) { return toupper(boost::io::get(src)); }
   };

and its cousins.
...
int main() {
  fstream("input.txt") > Filter(ToUpper);
}
This won't work, since fstream("input.txt") produces a temporary object which
cannot be used to initialize a non-const reference. Therefore operator< would
have to be declared to take a const reference, and the non-const extraction
functions would not be usable.

I have to go no, but I'll continue this discussion later.
...
Christopher Diggins
http://www.cdiggins.com
Jonathan