Noob needs help with macro

Hi, that's a small part of my code

Code:

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#define PAIRSUM(d1, d2) (d1-48)*10+(d2-48)    //macro at the top

        while (element < 3)
        {
          printf("Please enter number your credit card number ");
          scanf("%c%c%c%c%c%c%c%c%c%c", &d1[element], &d2[element], &d3[element], &d4[element], &d5[element],
          &d6[element], &d7[element], &d8[element], &d9[element], &d10[element]);
          sum_of_pairs[element] = PAIRSUM (d1[element],d2[element]) + PAIRSUM (d3[element],d4[element]) +
          PAIRSUM (d5[element],d6[element]) + PAIRSUM (d7[element],d8[element]) + PAIRSUM (d9[element],d10[element]);
          mod_result[element] = sum_of_pairs[element] % 26;
          vchar[element] = 'A' + mod_result[element];
          ++element;
        }

---

After first entry, everything is working fine and all results are good; however, every next input by the user for some reason decreases the input by 1 digit and messes up the results.

I'm pretty sure that when using arrays, the macro should be modified?

PS. arrays are just so I can print report of all input/results at the end.

Thanks in advance

I have no idea what you're doing but try this:

Code:

---

#define PAIRSUM(d1, d2) ((d1-48)*10+(d2-48))    //macro at the top

---

> #define PAIRSUM(d1, d2) (d1-48)*10+(d2-48) //macro at the top
1. Use '0' rather than 48 (if that is what you mean).
2. Code macros are extremely sensitive to lots of obscure operator precedence problems, depending on how you use them. It is therefore typical to parenthesise everything in a macro
Eg
#define PAIRSUM(d1, d2) (((d1)-'0')*10+((d2)-'0')) //macro at the top

> scanf("%c%c%c%c%c%c%c%c%c%c",
Unlike all the other conversions, %c does NOT skip white space / newlines. What you end up with is '\n' stored in the first character of the 2nd line of input.

Use fgets() to read a line, then sscanf to extract.

Code:

---

          char buff[BUFSIZ];
          printf("Please enter number your credit card number ");
          fgets( buff, sizeof buff, stdin );
          sscanf(buff, "%c%c%c%c%c%c%c%c%c%c", &d1[element], &d2[element], &d3[element], &d4[element], &d5[element],
          &d6[element], &d7[element], &d8[element], &d9[element], &d10[element]);

---

Thanks for the replies; unfortunately, the problem still exists.

when the user inputs first code number (10digit), I'm getting the results I want (code, remainder, pairsum, and encryption scheme symbol. The problem is when the loop goes back and takes another code... that's when I'm getting some crazy unrelated results.

Is there a bug in the loop? how can there be one, if the first entry always work?

PS. fgets() don't make any difference.

I don't think this will be of any help, but here is how I'm reading the results

Code:

---

howmany = element;
          printf("\nInput Code    10 Digit Sum Code        Code Value    Code With Symbol");
          printf("\n------------*----------------------*----------------*-------------------\n");
          for ( element = 0; element < howmany; element++)
          {
        printf("%c%c%c%c%c%c%c%c%c%c%15d%21d%13c%c%c%c%c%c%c%c%c%c%c",d1[element], d2[element], d3[element], d4[element], d5[element],
                d6[element], d7[element], d8[element], d9[element], d10[element], sum_of_pairs[element], mod_result[element], d1[element], d2[element],
                d3[element], d4[element], d5[element], d6[element], d7[element], d8[element], d9[element], d10[element], vchar[element]);
          }

---

You need to post a compilable program which shows the problem then.

this is only a fragment of the program so to eliminate confusion I made this part as the whole thing:

Code:

---

#include <stdio.h>
/********************************** Constants *******************************/

#define PAIRSUM(d1, d2) (((d1) - '0')*10+((d2) - '0'))
#define MY_NAME "XXXXXXXXXX"
#define SIZE 10                                                                  /* Size of array */

int main(void)
{

/********************************** Variables *******************************/

        char                d1[SIZE],
                                d2[SIZE],
                                d3[SIZE],
                                d4[SIZE],
                                d5[SIZE],
                                d6[SIZE],
                                d7[SIZE],
                                d8[SIZE],
                                d9[SIZE],
                                d10[SIZE],
                                vchar[SIZE],
                                howmany,
                                element;                        //element in an array
                               

        int                        sum_of_pairs[SIZE],
                                mod_result[SIZE];


    printf("\n************ ");
    printf(MY_NAME);
    printf(" presents XXXXXXXXXXXXXX Program ************\n\n");

       
        for ( element =0; element < 5; element++)
        {
          printf("Please enter number your credit card number ");
          scanf("&#37;c%c%c%c%c%c%c%c%c%c",&d1[element],&d2[element],&d3[element],&d4[element],&d5[element],&d6[element],&d7[element],&d8[element],&d9[element],&d10[element]);
          sum_of_pairs[element] = PAIRSUM (d1[element],d2[element]) + PAIRSUM (d3[element],d4[element]) +
          PAIRSUM (d5[element],d6[element]) + PAIRSUM (d7[element],d8[element]) + PAIRSUM (d9[element],d10[element]);
          mod_result[element] = sum_of_pairs[element] % 26;
          vchar[element] = 'A' + mod_result[element];
        }
    howmany = element;
        printf("\nInput Code    10 Digit Sum Code        Code Value    Code With Symbol");
        printf("\n------------*----------------------*----------------*-------------------\n");
        for ( element = 0; element < howmany; element++)
        {
      printf("%c%c%c%c%c%c%c%c%c%c%15d%21d%11c%c%c%c%c%c%c%c%c%c%c",d1[element],d2[element],d3[element],d4[element],d5[element],
          d6[element],d7[element],d8[element],d9[element],d10[element],sum_of_pairs[element],mod_result[element],d1[element],d2[element],
          d3[element],d4[element],d5[element],d6[element],d7[element],d8[element],d9[element],d10[element],vchar[element]);
        }
        printf("\n------------------------------------------------------------------------\n");

        fflush(stdin);
        printf("\nPress any key to terminate . . . \n");
        getchar();
    return 0;
}

---

now to verify, when you input 0000000000 then symbol should be A, when you input 5555345400 the symbol should be Q.

Thanks bro,

can somebody compile it and tell me what's wrong? pretty please?

Code:

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scanf("%c%c%c%c%c%c%c%c%c%c\n",
fflush(stdin); don't do that see faq.

---

Quote:

---

Originally Posted by robwhit

Code:

---

scanf("%c%c%c%c%c%c%c%c%c%c\n",
fflush(stdin); don't do that see faq.

---

---

where did you found that first line in my code?

fflush is a requirement...

Code:

---

scanf("%c%c%c%c%c%c%c%c%c%c",&d1[element],&d2[element],&d3[element],&d4[element],&d5[element],&d6[element],&d7[element],&d8[element],&d9[element],&d10[element]);

---

Quote:

---

fflush is a requirement...

---

It is not defined. Its behavior is fully implementation dependent. Could work, could not... Use some methods that always work

Quote:

---

Originally Posted by vart

Code:

---

scanf("%c%c%c%c%c%c%c%c%c%c",&d1[element],&d2[element],&d3[element],&d4[element],&d5[element],&d6[element],&d7[element],&d8[element],&d9[element],&d10[element]);

---

It is not defined. Its behavior is fully implementation dependent. Could work, could not... Use some methods that always work

---

what is wrong with this first line?

fflush what my proff want us to use, that's what I meant by requirement

As was said - your scanf leaves the new line in the buffer
so use fgets or add \n to the format:

scanf("%c%c%c%c%c%c%c%c%c%c\n",

Quote:

---

fflush what my proff want us to use,

---

He is wrong - on the ANSI C this does not solve your problem - use methods mentioned above

ok thanks, will try that, and argue with him about fflush:D

Appreciate all the help

To clarify a bit:

flushing *OUTPUT* streams is fine. Flushing the *INPUT* streams is what is not supported as part of ANSI C.

It may be supported on YOUR (or your professor's), compiler, but it isn't supported by the standard, and isn't supported by other C, ANSI compliant, compilers.

so that function should do the trick and be supported with ANSI C?

Code:

---

void flush(void)
{
        int ch;
        do
          ch = getchar();
        while (ch != EOF && ch != '\n');
        clearerr(stdin);
}

---

what would that possibly accomplish?