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

From: Peter Dimov (pdimov_at_[hidden])
Date: 2005-01-13 10:41:26

christopher diggins wrote:
> 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;
> }

IMO, this is how a more realistic example would look like:

void consume( string const & s, ostream & out )
{
    out << s;
}

string produce( istream & in )
{
    string ret;
    in >> ret;
    return ret;
}

// Transform as above

void do_transform( istream & in, ostream & out )
{
    while( !in.eof() )
    {
        consume( Transform( produce(in) ), out );
    }
}

int main()
{
    do_transform( cin, cout );
}

This is just a reflection of the general "globals are bad" principle.