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

From: christopher diggins (cdiggins_at_[hidden])
Date: 2005-01-13 10:19:21

----- Original Message ----- 
From: "Jonathan Turkanis" <technews_at_[hidden]>
>
> It's not that I don't see the benefit of lower complexity; I don't really 
> see
> the lower complexity. ;-)
>
> The only noticeable difference is that mine contains "template<typename 
> Source>"
> and uses a non-member get function.

And the facts that:
1) ToUpper() is not a non-member function
2) ToUpper() uses cin rather than a passed argument

Nonetheless consider the following psuedo-program (which does model a lot of 
software):

void Fu(string s) {
  cout << s;
}

string Bar() {
  string ret;
  cin >> ret;
  return ret;
}

string Transform(string s) {
  string ret(s);
  // do some stuff
  return ret;
}

void DoTransform() {
  while (!cin.eof()) {
    Fu(Transform(Bar()));
  }
}

int main() {
  DoTransform();
  return 0;
}

Now if at a later point I want to refactor and reuse the code from a program 
like this in another, I can either rewrite the entire program as an 
iostreams filter (which is not trivial), or I can simply write (using my 
personal library):

int main() {
  fstream("in.txt") > Filter(DoTransform) > fstream("out.txt");
}

Irregardless of the arguments for using iostreams filters (which trust me, I 
am very aware of), most of the time I am simply going to opt to use this 
syntax, because it require far less work.

Christopher Diggins
Object Oriented Template Library (OOTL)
http://www.ootl.org