Could anyone possibly help...?

[Nerdrage23]

Hello. I am working on a program that needs to, using a map, count every time a word occurs in a text document. The real issue that I am facing is how to read in the words from the text file. I understand the std::ifstream, I just don't know how to 'use' it. Any help on how to take in the text file and count the words would be great. Again, thanks!!

[Cubbi]

You can use it with the extraction operator, that is operator>>

#include <fstream>
#include <string>
#include <map>
#include <iostream>

int main()
{
    std::ifstream file("test.txt");
    std::map<std::string, unsigned> m;
    for(std::string word; file >> word; )
        ++m[word];

    for(auto& p: m)
        std::cout << "The word '" << p.first << "' was found " << p.second << " times\n";
}

[Nerdrage23]

What does ('auto& p': m) mean? I know that it is something that everyone keeps referencing in a few of my classes but I have never really looked into using it. Is it something along the lines of a generic? Or something entirely different?

[Cubbi]

Just a loop going over every element of a container. There are several ways to write that, this is the simplest.

[Nerdrage23]

So, its like an iterator? Just without all the excess typing?

[Nerdrage23]

I also have one last question:
With every word that I take in, is their a way that I can make sure that every character in the word is lower case? Isn't their something in the stl that does that for me?

[Cubbi]

sure, there are plenty of ways to lowercase every letter of a word:

loop (range-for, iterator-based, or indexed, e.g.)

for(auto& c: word)
    c = std::tolower(c);

for_each
std::for_each(word.begin(), word.end(), [](char& c){ c = std::tolower(c); });

transform, which might be a bit wordy:

 std::transform(word.begin(), word.end(), word.begin(),
                  [](char c){return std::tolower(c); });

or, 1998 textbook style,

    std::transform(word.begin(), word.end(), word.begin(),
                   static_cast<int(*)(int)>(std::tolower));

or even the rarely-used ctype:
std::use_facet<std::ctype<char>>(std::locale()).tolower(&word[0], &word[0] + word.size());

finally, there's always boost:
boost::algorithm::to_lower(word);

which could be incorporated in that program I first wrote in its to_lower_copy version:

   for(std::string word; file >> word; )
        ++m[boost::algorithm::to_lower_copy(word)];