New to C++

[gbman88]

Hi all I am having some problems with compiling my c++ code. I have had lots of experience in Java but c++ is new.

I am trying to read in a file that contains words, sort them, then print them out to a new file in my program but the error is saying there is error on line 22 involving iterating through the elements of a vector. I am confused and any help is greatly appreciated!

#include <iostream>
#include <list>
#include <fstream>
#include <string>

using namespace std;

int main() {
string x;
list<string> myList;
ifstream inFile;
ofstream outFile;

inFile.open("dictionary");
	while (inFile >> x) {
		myList.push_back(x);
	}
	inFile.close();
	myList.sort();
	outFile.open("sortedDictionary");
	for (int i = 0; i < myList.size(); i++) {
			outFile << myList[i] << endl;
		}
		outFile.close();
		return 0;
	}

[Sebastiani]

Hi all I am having some problems with compiling my c++ code. I have had lots of experience in Java but c++ is new.

I am trying to read in a file that contains words, sort them, then print them out to a new file in my program but the error is saying there is error on line 22 involving iterating through the elements of a vector. I am confused and any help is greatly appreciated!

#include <iostream>
#include <list>
#include <fstream>
#include <string>

using namespace std;

int main() {
string x;
list<string> myList;
ifstream inFile;
ofstream outFile;

inFile.open("dictionary");
    while (inFile >> x) {
        myList.push_back(x);
    }
    inFile.close();
    myList.sort();
    outFile.open("sortedDictionary");
    for (int i = 0; i < myList.size(); i++) {
            outFile << myList[i] << endl;
        }
        outFile.close();
        return 0;
    }

std::list has no operator []. Replace it with an std::vector and it'll work fine. Otherwise, just change the loop to:

for (list< string >::const_iterator it = myList.begin( ), end = myList.end( ); it != end; it++) {
            outFile << *it << endl;
        }

Incidentally, the above code works with virtually every type of container, so that idiom is most preferable...

[whiteflags]

In my opinion, the error is clear:

Compiling: main.cpp
C:\Documents and Settings\Owner\My Documents\sandbox\sandbox\main.cpp: In function 'int main()':
C:\Documents and Settings\Owner\My Documents\sandbox\sandbox\main.cpp:23:37: warning: comparison between signed and unsigned integer expressions
C:\Documents and Settings\Owner\My Documents\sandbox\sandbox\main.cpp:25:28: error: no match for 'operator[]' in 'myList[i]'
Process terminated with status 1 (0 minutes, 1 seconds)
1 errors, 1 warnings

You can fix everything by using iterators:

 for ( std::list<std::string>::iterator i = mylist.begin(); i != mylist.end(); ++i) ...

std::list doesn't support random access because it models a linked list and linked lists don't have random access.

[gbman88]

Wow thanks all! Its been a long day and I seemed to have forgotten I was dealing with a list and not a vector. Thanks for pointing out the obvious mistake.

[CommonTater]

I hope nobody minds, but I "borrowed" this and tried it myself... got it working with the iterators as suggested...

Now, if I was using a vector <string> instead of the list.... how would I sort that?

[Sebastiani]

I hope nobody minds, but I "borrowed" this and tried it myself... got it working with the iterators as suggested...

Now, if I was using a vector <string> instead of the list.... how would I sort that?

std::sort.

[CommonTater]

See... now that was too easy...

#include <iostream>
#include <algorithm>
#include <vector>
#include <fstream>
#include <string>

using namespace std;

int main()
  { ifstream inFile;
    vector<string> myList;
    string x;
    inFile.open("test.txt");
    while (inFile >> x)
      { myList.push_back(x); }
    inFile.close();

    sort(myList.begin(),myList.end());

    ofstream outFile;
    outFile.open("words.txt");            
    for (int i = 0; i != myList.size(); i++)
      {	outFile << *i << endl;
        cout << myList[i] << endl;  }
    outFile.close();
    return 0; }

[Sebastiani]

See... now that was too easy...

#include <iostream>
#include <algorithm>
#include <vector>
#include <fstream>
#include <string>

using namespace std;

int main()
  { ifstream inFile;
    vector<string> myList;
    string x;
    inFile.open("test.txt");
    while (inFile >> x)
      { myList.push_back(x); }
    inFile.close();

    sort(myList.begin(),myList.end());

    ofstream outFile;
    outFile.open("words.txt");            
    for (int i = 0; i != myList.size(); i++)
      {    outFile << *i << endl;
        cout << myList[i] << endl;  }
    outFile.close();
    return 0; }

>> outFile << *i << endl;

Except...'i' is an int.

Here's yet another way to do it, by the way:

#include <iostream>
#include <fstream>
#include <string>
#include <vector>
#include <iterator>
int main()
{ 
    using namespace std;
    ifstream inFile("test.txt");
    vector<string> myList;
    copy(istream_iterator<string>(inFile), istream_iterator<string>(), back_inserter(myList));
    sort(myList.begin(), myList.end());
    ofstream outFile("words.txt");            
    copy(myList.begin(), myList.end(), ostream_iterator<string>(outFile, "\n"));
    return 0; 
}

[CommonTater]

>> outFile << *i << endl;

Except...'i' is an int.

Oh crap... I have it working but I must have copied that to the clipboard before I commented that line out... ... such is life...