Question

First off, thanks in advance for your help. This issue is driving me nuts.

I have a program that accepts a c-string, and then can count the number of vowels and consonants. This works without issue. However, I also need to include a function that allows the user to create a new string. The problem is, though, when the user selects “new string” from the menu, it just loops through the newString() method, without waiting for the user’s input. It then creates a new, blank screen.

Here is the entire program. The newString() method is at the end.

#include <iostream>    
using namespace std;

// function prototype
void printmenu(void);
int vowelCount(char *);
int consCount(char *);
int cons_and_vowelCount(char *);
void newString(char *, const int);

int main() {

    const int LENGTH = 101;
    char input_string[LENGTH];      //user defined string
    char choice;                        //user menu choice
    bool not_done = true;       //loop control flag

    // create the input_string object
    cout << "Enter a string of no more than " << LENGTH-1 << " characters:\n";
    cin.getline(input_string, LENGTH);

    do {
        printmenu();
        cin >> choice;
        switch(choice)
        {
            case 'a':
            case 'A':
               vowelCount(input_string);
               break;
            case 'b':
            case 'B':
               consCount(input_string);
               break;
            case 'c':
            case 'C':
                cons_and_vowelCount(input_string);
                break;
            case 'd':
            case 'D':
               newString(input_string, LENGTH);
               break;
            case 'e':
            case 'E':
               exit(0);
            default:
                cout << endl << "Error: '" << choice << "' is an invalid selection" << endl;
                break;
        } //close switch
    } //close do

while (not_done);
return 0;
} // close main

/* Function printmenu()
 * Input:
 *  none
 * Process:
 *  Prints the menu of query choices
 * Output:
 *  Prints the menu of query choices
 */
void printmenu(void)
{
    cout << endl << endl;
    cout << "A) Count the number of vowels in the string" << endl;
    cout << "B) Count the number of consonants in the string" << endl;
    cout << "C) Count both the vowels and consonants in the string" << endl;
    cout << "D) Enter another string" << endl;
    cout << "E) Exit the program" << endl;
    cout << endl << "Enter your selection: ";
    return;    
}

int vowelCount(char *str) {
    char vowels[11] = "aeiouAEIOU";
    int vowel_count = 0;

    for (int i = 0; i < strlen(str); i++) {
        for (int j = 0; j < strlen(vowels); j++) {
            if (str[i] == vowels[j]) {
                vowel_count++;
            }
        }
    }
    cout << "String contains " << vowel_count << " vowels" << endl;
    return vowel_count;
} // close vowelCount

int consCount(char *str) {
    char cons[43] = "bcdfghjklmnpqrstvwxyzBCDFGHJKLMNPQRSTVWXYZ";
    int cons_count = 0;

    for (int i = 0; i < strlen(str); i ++) {
        for (int j = 0; j < strlen(cons); j++) {
            if (str[i] == cons[j]) {
                cons_count++;
            }
        }
    }
    cout << "String contains " << cons_count << " consonants" << endl;
    return cons_count;
} // close consCount

int cons_and_vowelCount(char *str) {
    int cons = consCount(str);
    int vowels = vowelCount(str);
    int total = cons + vowels;

    cout << "The string contains a total of " << total << " vowels and "
            "consonants" << endl;
    return total;
}

void newString(char *str, int len) {
    cout << "Enter a string of no more than " << len-1 << " characters:\n";
    cin.getline(str, len);
    return;
}

Answer 1

The statement cin >> choice only consumes the character they type, not the carriage return that follows. Thus, the subsequent getline() call reads an empty line. One simple solution is to call getline() instead of cin >> choice and then use the first character as the choice.

BTW, the while (not done) should immediately follow the do { … }, and the return 0 is redundant. Also, you should call newString at the start of the program instead of repeating its contents.