I give up, here is my code, please help

hubabuba · 01-29-2005, 12:29 PM

I'm posting the code of my program and the messages the compiler gives. I spent almost 2 days to find the problems, but couldn't, I don't understand arrays and pointer well.

Code:

#include <stdio.h>
#include <string.h>

#define BUFSIZE 256
#define TRUE 1
#define FALSE 0

char getISBN(char ISBN[]);

char checkDigitFromISBN(const char ISBN[]);

void getPartISBNFromISBN(char PartISBN[], const char ISBN[], unsigned nChars);

unsigned digitFromCharacter(char ch);

char characterFromDigit(unsigned digit);

char calculateCheckDigit(const char PartISBN[]);

int checkDigitAreEqual(char claculatedCheckDigit, char theCheckDigit);

int main(void)
{
  char string[BUFSIZ], part[BUFSIZ], isbn[BUFSIZ], checkDigit[BUFSIZ], calculate[BUFSIZ];
  
  strncpy(isbn, getISBN(string), 11);
  
  strncpy(checkDigit, checkDigitFromISBN(isbn), 2);
  
  getPartISBNFromISBN(part, isbn, 10);
  
  strncpy(calculate, calculateCheckDigit(part), 2);
  
  if(checkDigitAreEqual(calculate, checkDigit) == 0)
    printf("The number entered is not a valid ISBN\n");
  else if(checkDigitAreEqual(calculate, checkDigit) == 1)
    printf("ISBN is OK\n"); 
}

char getISBN(char ISBN[])
{   
  printf("Enter the ISBN number: ");
  fgets(ISBN, BUFSIZE, stdin);
  return ISBN;
}
  
char checkDigitFromISBN(const char ISBN[])
{
  return ISBN[9];
}
   
void getPartISBNFromISBN(char PartISBN[], const char ISBN[], unsigned nChars)
{
  strncpy(PartISBN, ISBN, nChars);
}

unsigned digitFromCharacter(char ch)
{
  return (unsigned)ch - '0';
}

char characterFromDigit(unsigned digit)
{
  return (char)digit + '0';
}

char calculateCheckDigit(const char PartISBN[])
{
  unsigned i = 0u;
  unsigned integer;
  unsigned weight = 10u;
  unsigned partSum;
  unsigned total;
  unsigned remainder;
  unsigned check;
  char character;
     
  while(PartISBN[i] != NULL)
  {
     integer = digitFromCharacter(PartISBN[i]);
     partSum = integer * weight;
     i++;
     weight--;
     total = total + partSum;
  }
  
  remainder = total % 11;
  
  check = 11 - remainder;
  
  return character = characterFromDigit(check);
}
 
int checkDigitAreEqual(char calculatedCheckDigit, char theCheckDigit)
{
  if(calculatedCheckDigit == theCheckDigit)
    return TRUE;
  else
    return FALSE;
}

COMPILER MESSAGES:
[root@dhcppc2 prog]# cc -o prog prog6.c
prog6.c: In function `main':
prog6.c:26: warning: passing arg 2 of `strncpy' makes pointer from integer without a cast
prog6.c:28: warning: passing arg 2 of `strncpy' makes pointer from integer without a cast
prog6.c:32: warning: passing arg 2 of `strncpy' makes pointer from integer without a cast
prog6.c:34: warning: passing arg 1 of `checkDigitAreEqual' makes integer from pointer without a cast
prog6.c:34: warning: passing arg 2 of `checkDigitAreEqual' makes integer from pointer without a cast
prog6.c:36: warning: passing arg 1 of `checkDigitAreEqual' makes integer from pointer without a cast
prog6.c:36: warning: passing arg 2 of `checkDigitAreEqual' makes integer from pointer without a cast
prog6.c: In function `getISBN':
prog6.c:44: warning: return makes integer from pointer without a cast
prog6.c: In function `calculateCheckDigit':
prog6.c:78: warning: comparison between pointer and integer

Hko · 01-29-2005, 01:12 PM

OK. I was not able to understand what each function is supposed to do. (or more honestly, I didn't feel like figuring it all out from your code).

So I fixed the code up so it compiles without errors. But I think my "fixing" will have also destroyed the way it's supposed to work. Especially the supossed result of the function "calculateCheckDigit()" was quite unclear to me. Sorry to say it this way, but your code has quite a few mistakes, and my "fixed" version still has most of them. It didn't feel like figuring out how ISBN-numbers are formatted and how your program tries to check them.

But now at least it compiles without errors. Hope I could help a litle this way.
Most of the errors had to do with your code assuming a char is the same as a char* (i.e. a string), which is not the case (in C) and resulted in compiler errors.

Code:

#include <stdio.h>
#include <string.h>

#define BUFSIZE 256
#define TRUE 1
#define FALSE 0

char *char2str(char c);
char *getISBN(char ISBN[]);
char *checkDigitFromISBN(const char ISBN[]);
void getPartISBNFromISBN(char PartISBN[], const char ISBN[], unsigned nChars);
unsigned digitFromCharacter(char ch);
char characterFromDigit(unsigned digit);
char *calculateCheckDigit(const char PartISBN[]);
int checkDigitAreEqual(char claculatedCheckDigit, char theCheckDigit);

int main(void)
{
    char string[BUFSIZ], part[BUFSIZ], isbn[BUFSIZ], checkDigit[BUFSIZ],
        calculate[BUFSIZ];

    strncpy(isbn, getISBN(string), 11);
    strncpy(checkDigit, checkDigitFromISBN(isbn), 2);
    getPartISBNFromISBN(part, isbn, 10);
    strncpy(calculate, calculateCheckDigit(part), 2);

    if (checkDigitAreEqual(calculate[0], checkDigit[0]) == 0)
        printf("The number entered is not a valid ISBN\n");
    else if (checkDigitAreEqual(calculate[0], checkDigit[0]) == 1)
        printf("ISBN is OK\n");

    return 0;
}

char *char2str(char c)
{
    /* Dirty hack, but works in this case. */
    static char str[2];
    str[0] = c;
    str[1] = '\0';
    return str;
}

char *getISBN(char ISBN[])
{
    printf("Enter the ISBN number: ");
    fgets(ISBN, BUFSIZE, stdin);
    return ISBN;
}

char *checkDigitFromISBN(const char ISBN[])
{
    return char2str(ISBN[9]);
}

void getPartISBNFromISBN(char PartISBN[], const char ISBN[], unsigned nChars)
{
    strncpy(PartISBN, ISBN, nChars);
}

unsigned digitFromCharacter(char ch)
{
    return (unsigned) ch - '0';
}

char characterFromDigit(unsigned digit)
{
    return (char) digit + '0';
}

char *calculateCheckDigit(const char PartISBN[])
{
    unsigned i = 0u;
    unsigned integer;
    unsigned weight = 10u;
    unsigned partSum;
    unsigned total;
    unsigned remainder;
    unsigned check;
    /* char character; */  /* removed */

    while (PartISBN[i] != '\0') {
        integer = digitFromCharacter(PartISBN[i]);
        partSum = integer * weight;
        i++;
        weight--;
        total = total + partSum;
    }

    remainder = total % 11;

    check = 11 - remainder;

    return char2str(characterFromDigit(check));
}

int checkDigitAreEqual(char calculatedCheckDigit, char theCheckDigit)
{
    if (calculatedCheckDigit == theCheckDigit)
        return TRUE;
    else
        return FALSE;
}