| re: Searching text files
"John Harrison" <john_andronicus@hotmail.com> wrote in message news:<bedlv0$3rup5$1@ID-196037.news.dfncis.de>...[color=blue]
> "hivie" <hivie2000@yahoo.com> wrote in message
> news:49fd2f82.0307072129.7c1f3954@posting.google.c om...[color=green]
> > I have a problem that is causing me problems. I have a text file that
> > stores 5 lines of crap (stuff that I dont need( for the user only)).
> > After that there is data that is in three columns separated by lots of
> > whitespace. I dont think that the bytes are uniform ( I tried
> > TextReader.readblock). Sorry, I am using VC++ .net. I only need the
> > first two columns that are both double values. I need to either read
> > those two columns into a mulit-Dim array or be able to search the
> > file expeditously at runtime. The searchable value is the value in
> > the first column. Can someone give some direction please???
> > Thank you
> >
> > hivie[/color]
>
> What is TextReader.readblock? You'll only get a answer in standard C++ here.
>
> What's in the third column? This is going to have to be read, even though
> you don't need it.
>
> Your searching requirements would be best dealt with using a std::map
>
> #include <map>
>
> std::map<double, double> my_map;
>
> Much, much more efficient than an array. If you need to hold duplicate
> values for the first column, then use a multi_map instead of a map.
>
> Something like this? (untested)
>
> #include <fstream>
> #include <string>
> #include <map>
>
> ifstream my_file("myfile.txt");
> std::map<double, double> my_map;
> string dummy;
> // skip file lines
> for (int i = 0; i < 5; ++i)
> getline(my_file, dummy);
> double col1, col2;
> while (my_file >> col1 >> col2)
> {
> my_map[col1] = col2;
> if (!getline(my_file, dummy)) // skip rest of line
> break;
> }
>
> You should investigate map::lower_bound, map::upper_bound and
> map::equal_range for searching the map. Searching a map, whose key is a
> double, for exact values is unlikely to work.
>
> john[/color]
Sorry, the textreader is a .net thing. I have never heard of "map",
but I am going to look into it. thanks for the direction!
Heath
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