How to use function definitions to open, read, and close a file - c++

Question

We are asked to open a text file that contains a sentence and go through all the letters and whitespace in the file and count how many of each ascii character there are.
When I had all my information in the main function it worked fine. I just can't figure out how to call them all successfully in the main. The output should look like:
15 words
6 a
3 d
6 e
3 g
3 h
3 i
15 l
6 o
6 r
3 s
3 t
3 w
I achieved this output when again everything was in the main function so now it's just a matter of getting it like this with my function definitions.
My Code:
#include <iostream>
#include <fstream>
#include <string>
using namespace std;
//prototypes
//int openFile();
void readFile(ifstream &in);
void closeFile(ifstream &in);
//definitions
int openFile()
{
ifstream in;
in.open("word_data.txt");
}
void readFile(ifstream &in)
{
//store the frequency of the letters
int letters[128];
//declare variables
char let;
int wordCount = 0;
//for loop to initialize all counts to zero
for (int i = 0; i < 128; i++)
{
letters[i] = 0;
}
//get letters until we reach end of file
//whitespace = wordCount++;
let = in.get();
while (let != EOF)
{
if (let == ' ')
wordCount++;
//change to lowercase
let = tolower(let);
letters[let]++;
let = in.get();
}
//output
//num words
cout << wordCount + 1 << " words" << endl;
//count how many of each letter there are & print to screen in alphabetical order
for (char let = 'a'; let <= 'z'; let++)
{
if (letters[let] != 0)
{
cout << letters[let] << " "<< let <<endl;
}
}
}
void closeFile(ifstream &in)
{
in.close();
}
int main()
{
openFile();
readFile(in);
closeFile(in);
return 0;
}

Answer 1

The problem is with your openFile() function. It creates a local ifstream only, it does not open an ifstream that is accessible to the other functions.
Try this instead:
#include <iostream>
#include <fstream>
#include <string>
#include <cctype>
using namespace std;
//prototypes
void openFile(ifstream &in);
void readFile(ifstream &in);
void closeFile(ifstream &in);
//definitions
void openFile(ifstream &in)
{
in.open("word_data.txt");
}
void readFile(ifstream &in)
{
//store the frequency of the letters
int letters[128] = {};
//declare variables
char ch;
int wordCount = 0;
//get letters until we reach end of file
while (in.get(ch))
{
if (ch == ' ')
wordCount++;
//change to lowercase
ch = static_cast<char>(tolower(static_cast<unsigned char>(ch)));
letters[ch]++;
}
//output
//num words
cout << wordCount + 1 << " words" << endl;
//count how many of each letter there are & print to screen in alphabetical order
for (ch = 'a'; ch <= 'z'; ch++)
{
if (letters[ch] != 0)
{
cout << letters[ch] << " " << ch <<endl;
}
}
}
void closeFile(ifstream &in)
{
in.close();
}
int main()
{
ifstream in;
openFile(in);
readFile(in);
closeFile(in);
return 0;
}
With that said, you might consider using a std::map to track your frequencies, rather than using an int[] array. And using operator>> to read whole words at a time:
#include <map>
...
void readFile(ifstream &in)
{
//store the frequency of the letters
map<char, int> letters;
//declare variables
string word;
int wordCount = 0;
//get letters until we reach end of file
while (in >> word)
{
++wordCount;
//for(size_t idx = 0; idx < word.size(); ++idx)
//{
// char ch = word[idx];
for(char ch : word)
{
//change to lowercase
ch = static_cast<char>(tolower(static_cast<unsigned char>(ch)));
if (ch >= 'a' && ch <= 'z')
letters[ch]++;
}
}
//output
//num words
cout << wordCount << " words" << endl;
//count how many of each letter there are & print to screen in alphabetical order
//for (map<char, int>::iterator iter = letters.begin(); iter != letters.end(); ++iter)
//{
// cout << iter->second << " " << iter->first << endl;
//}
for (auto &elem : letters)
{
cout << elem.second << " " << elem.first << endl;
}
}