No clue how to deal with this error

[holyheck]

I'm trying to make a program which gives me all the words that have a certain number of letters, it gives me the error: "invalid conversion from 'char' to 'const char*' [-fpermissive]". I have googled and searched around for a solution and have read the references but I don't know what to change.

#include <iostream>
#include <fstream>
#include <math.h>
#include <string.h>


using namespace std;

int main()
{
    ifstream f("words.txt");
    int nr_words;
    f >> nr_words;            //first line of the txt file is the nr of words
    char v[nr_words];

    for(int i=1; i<nr_words; i++)
    {
        f >> v[i];
        cout<<v[i]<<" ";
    }

    cout<<endl;
    cout<<endl;

    int nr_letters;
    cout<<"number of letters the word has: ";
    cin>>nr_letters;

    for(int i=1; i<nr_words; i++)
    {
        if(strlen(v[i])==nr_letters)
            cout<<v[i];
    }


    return 0;
}

[Repeater]

The function strlen accepts an input parameter of type char-pointer.

v[i] is a char.

See the difference. It wants a char-pointer, you're passing it a char.

A char-pointer is not the same thing as a char.

[Repeater]

Nothing you do here makes any sense.

char v[nr_words];
This creates an array of char. Each char can hold ONE letter. Yet you seem to be trying to store entire words in them. This makes no sense.

[Repeater]

Ah, I see you had this problem before and you've ignored what I said last time: http://www.cplusplus.com/forum/beginner/238999/

[nuderobmonkey]

At line 14 you define an array of single 'char'-types. but in line 19 you're probably try reading a whole c-string word into a single 'char' storage space!

You could expand your 'char' array at line 14 to a 2-dimensional type: char v[nr_words][32];

But be aware that using raw arrays for is error prone. c++ offers better alternatives. Here a suggestion by using std::vector and std::string objects:

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

using namespace std;

int main()
{
    ifstream f("words.txt");
    if (!f) 
    {
        cerr << "Couldn't open file.";
        return 1;
    }

    int nr_words;
    f >> nr_words;

    vector<string> v(nr_words);

    for (int i = 0; i < nr_words; ++i) 
    {
        f >> v[i];
    }

    cout << "\n\n";

    size_t nr_letters;
    cout << "number of letters the word has: ";
    cin >> nr_letters;

    for ( string & word : v)
    {
        if (word.length() == nr_letters)
            cout << word;
    }

    return 0;
}

[icy1]

also, @holyheck, is there a reason you're trying to work with C-style strings? You're using C++ input/output operations, C++ file operations, and then suddenly C character arrays and related functions.

Many times when including with the angle brackets but providing a .h file, like #include <string.h> will bring in a file from the C standard lib (unless you have specific custom changes to your project's include directories). This can be made clearer by putting a "c" in front and removing the ".h", as in #include <cstring> or #include <cmath> . Readers now know you're specifically bringing in something from the C libs.

I'd try to avoid including C stuff altogether and use as many C++ libs as possible

#include <iostream>
#include <fstream>
#include <string>  // C++ std::string

using namespace std;

int main()
{
    string file_name("words.txt");
    // Just slightly clearer to name your variable to show it's not just any stream but an input file stream
    ifstream ifs(file_name);
    if (!ifs)
    {
        cout << "Unable to open \""<<file_name<<"\".  Please check it exists and not in use.\n";
        return -1;
    }

    int nr_letters;
    cout << "Letters in word? ";
    cin >> nr_letters;


    int nr_words;
    ifs >> nr_words;  // It's cool that your file has this at the top, but it's not really needed

    string word;
    while (ifs >> word)
    {
        // Do stuff if word.size() is correct...
    }

    return 0;
}