Using Pointers to pass C-String arguments

Question

I have been stuck on this program all day. I finally feel like I'm getting really close. I have to find the number of vowels and characters in a string. Then output them at the end. However, when I compile my program crashes. I have checked syntax and looked in my book all day. If anyone can help I would really appreciate it! because I have 5 more similar functions to write that manipulate c-strings. Thanks!

#include <iostream>
#include <string>
using namespace std;

int specialCounter(char *, int &);


int main()
{

const int SIZE = 51;        //Array size
char userString[SIZE];      // To hold the string
char letter;
int numCons;



// Get the user's input string
cout << "First, Please enter a string (up to 50 characters): " << endl;
cin.getline(userString, SIZE);





// Display output
cout << "The number of vowels found is " << specialCounter(userString, numCons) <<      "." << endl;
cout << "The number of consonants found is " << numCons << "." << endl;


}



int specialCounter(char *strPtr, int &cons)
{
int vowels = 0;
cons = 0;


while (*strPtr != '/0')
{
    if (*strPtr == 'a' || 'A' || 'e' || 'E' || 'i' || 'I' || 'o' || 'O' || 'u' || 'U')
    {
        vowels++;       // if vowel is found, increment vowel counter
                    // go to the next character in the string
    }
    else
    {
        cons++;         // if consonant is found, increment consonant counter
                    // go to the next character in the string
    }

    strPtr++;

}
return vowels;

}

*strPtr == 'a' || 'A' || 'e' || 'E' || 'i' || 'I' || 'o' || 'O' || 'u' || 'U' will always be true because 'A' is not 0. — Qaz
– Qaz, Commented Feb 12, 2013 at 3:00
I'm not sure I understand because in the while I'm check for the '/0', the null terminator. — devnando
– devnando, Commented Feb 12, 2013 at 3:02
Are you looking for any specific bool condition from that expression? Hint: *strPtr == 'a' || *strPtr == 'A' || *strPtr == 'e'...... After you're done typing all of that, throw it out, put all your test chars in a single string constant (const char vowels[] = "aAeEiIoOuU";) and change your expression to if (strchr(vowels, *strPtr)) — WhozCraig
– WhozCraig, Commented Feb 12, 2013 at 3:02
Ohhh. Ok so I should not use the or || because its searching for all the vowels? Like instead use a switch statement for each char? — devnando
– devnando, Commented Feb 12, 2013 at 3:06
@user2063325, Personally, I would use std::count_if, but it's probably disallowed. See my answer for the proper way to compare against multiple conditions. — Qaz
– Qaz, Commented Feb 12, 2013 at 3:07

Qaz · Accepted Answer · 2013-02-12 03:04:03Z

3

I'm going to assume you're limited to not using std::string or std::getline and that you have to assume the user inputs something less than 51 characters.

Your crash stems from:

while (*strPtr != '/0')

A null character is an escape code. '/0' is a multicharacter literal with an implementation-defined value. That means it's probably always true. Change it to:

while (*strPtr != '\0') //or while (strPtr)

Apart from that, you have a logic error with your vowel check. You have to check it against each vowel, like this:

if (*strPtr == 'a' || *strPtr == 'e') //etc.

You'll find it easier if you compare against the toupper or tolower version of each character to reduce the number of comparisons by a factor of 2.

answered Feb 12, 2013 at 3:04

Qaz

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David Schwartz · Accepted Answer · 2013-02-12 03:04:24Z

2

while (*strPtr != '/0')

Should be:

while (*strPtr != 0)

or

while (*strPtr != '\0');

Didn't your compiler give you a warning? If so, don't ignore warnings. If not, get a better compiler.

See also the comments about the error in your other comparison.

answered Feb 12, 2013 at 3:04

David Schwartz

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1 Comment

devnando Over a year ago

Yea it didn't give me a warning. :/ . I can't believe I had the slash going the wrong way. Thanks so much!

billz · Accepted Answer · 2013-02-12 03:10:15Z

2

Other answers should fix your issue, may I suggest you write separate functions instead of one almighty function?

bool IsSpecialChar(char c)
{
 switch(c)
 {
    case 'a':
    case 'A':
    case 'e':
    case 'E':
    case 'i':
    case 'I':
    case 'o':
    case 'O':
    case 'u':
    case 'U':
    return true;
 }
   return false; 
}


int specialCounter(char *strPtr, int &cons)
{
  int vowels = 0;
  cons = 0;
  while (*strPtr != '\0')
  {
    IsSpecialChar(*strPtr) ? vowels++ : cons++;
    strPtr++;

  }
  return vowels;
}

answered Feb 12, 2013 at 3:10

billz

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