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

From: Rob Stewart (stewart_at_[hidden])
Date: 2005-01-13 12:35:16

From: christopher diggins <cdiggins_at_[hidden]>
> 
> 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);
> }
> 
> int main() {
>   fstream("input.txt") > Filter(ToUpper);
> }

In principle, the approach seems interesting.  It is the approach
that is being questioned here.  In fact, if the idea didn't
strike the fancy of anyone, you'd have gotten no discussion.

How well will your scheme work with a tens of megabytes file?  If
you have a great deal of memory on your machine, then make it
tens of gigabytes.  Eventually, your approach fails because each
stage of the pipeline must have a (possibly modified) copy of its
input.  Thus, there are at least two copies of the data in memory
at once.  Jonathan's library scales better, so if you can make
use of it, your library will scale better.

Perhaps your library providing some classes/functions to reduce
the requirements levied on users to achieve your goal.  IOW,
there might be a way to recast your ideas to eliminate reliance
on cin and cout and to avoid having to process all data at once.

-- 
Rob Stewart                           stewart_at_[hidden]
Software Engineer                     http://www.sig.com
Susquehanna International Group, LLP  using std::disclaimer;