letters.cpp

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#include <iostream>
#include <fstream>          // for ifstream
#include <cstdlib>          // for exit()
#include <cctype>           // for tolower()
#include <climits>          // for CHAR_MAX
#include <string>
#include <iomanip>
using namespace std;

#include "prompt.h"
#include "tvector.h"

// count # occurrences of all characters in a file
// written: 8/5/94, Owen Astrachan, modified 5/1/99

void Print(const tvector<int> & counts, int total);
void Count(istream & input, tvector<int> & counts, int & total);

int main()
{
    int totalAlph = 0;    
    string filename = PromptString("enter name of input file: ");
	ifstream input(filename.c_str());

    if (input.fail() )
    {   cout << "could not open file " << filename << endl;
        exit(1);
    }
    tvector<int> charCounts(CHAR_MAX+1,0);    // all initialized to 0
 
    Count(input,charCounts,totalAlph);
    Print(charCounts,totalAlph);
    
    return 0;
}

void Count(istream & input, tvector<int> & counts, int & total)
// precondition: input open for reading
//               counts[k] == 0, 0 <= k < CHAR_MAX
// postcondition: counts[k] = # occurrences of character k
//                total = # alphabetic characters     
{
    char ch;
    while (input.get(ch))               // read a character
    {   if (isalpha(ch))                // is alphabetic (a-z)?
        {   total++;
        }
        ch = tolower(ch);               // convert to lower case
        counts[ch]++;                   // count all characters
    }    
}

void Print(const tvector<int> & counts, int total)
// precondition: total = total of all entries in counts['a']..counts['z']
// postcondition: all values of counts from 'a' to 'z' printed     
{ 
    const int MIDALPH = 13;
    cout.setf(ios::fixed);    // print 1 decimal place 
    cout.precision(1);    
    char k;    
    for(k = 'a'; k <= 'm'; k++)
    {   cout << k << setw(7) << counts[k] << " ";
        cout << setw(4) << 100 * double(counts[k])/total << "% \t\t";
        cout << char(k+MIDALPH) << setw(7) << counts[k+MIDALPH] << " ";
        cout << setw(4) << 100 * double(counts[k+MIDALPH])/total << "%" << endl;
    }
}