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Re: C++ file processing


Justin Findlay <farquharsoncraig@yahoo.com> writes:

> Why doesn't ifstream overload operator>> for const
> char * types so that one could do this:
> 
> string keep_this_string;
> ifstream fin( "fin.txt" );
> while ( fin )
> {
>   fin >> "Ignore this string everywhere it occurs" >>
> keep_this_string >> "Ignore something else";

I am not at sure I understand. The primary stream use of the left hand
    argument of operator>> is a place to write the extracted data
    to. The secondary use is a manipulator which changes the
    formatting state of the stream. You seem to be suggesting a kind
    of operator>> which instead uses the right hand side as an
    indicator of what to ignore. This is not consistent with either
    the primary or secondary existing operator>> idioms. My second
    objection is that your notion seems fragile; IMO it is rare for a
    file format to both require that a piece of text exactly match a
    specific string, and then ignore it. 

Probably no-one thought of it. In any case, it needs to be better
    explained, and perhaps even then it would be deemed too
    confusing. I had to read your  several times to understand what
    you meant - assuming I understand it now.

>   use_it( keep_this_string.c_str() );
> }
> 
> How about an istream member getline() that returns a
> formatted string:
> 
> istringstream iline;
> iline.str( fin.getline() );
> iline >> "Ignore this string everywhere it occurs" >>
> keep_this_string >> "Ignore something else";
> use_it( keep_this_string.c_str() );
> 
> or even just:
> 
> string ilinestr;
> fin.getline( ilinestr );
[snip]

This suggestion I do not understand at all.


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