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printf does not work out of loop K&R array example

This is a discussion on printf does not work out of loop K&R array example within the C Programming forums, part of the General Programming Boards category; Code: #include <stdio.h> /* count digits, white space, others */ main() { int c, i, nwhite, nother; int ndigit[ 10 ...

  1. #1
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    printf does not work out of loop K&R array example

    Code:
    #include <stdio.h>
    /* count digits, white space, others */
    main()
    {
     int c, i, nwhite, nother;
     int ndigit[10];
    	nwhite = nother = 0;
     for (i = 0; i < 10; ++i)
    		ndigit[i] = 0;
     while ((c = getchar()) != EOF){
     if (c >= '0' && c <= '9')
    			++ndigit[c-'0'];
     else if (c == ' ' || c == '\n' || c == '\t')
    			++nwhite;
    else
    			++nother;
    	}
    printf("digits =");
     for (i = 0; i < 10; ++i)
     printf(" %d", ndigit[i]);
    printf(", white space = %d, other = %d\n",
    			   nwhite, nother);
    }
    

    this code an example for an array in K&R 2 but it is not executed unless printf inside the while loop is there a specific reason for that or may be something wrong with my mac ?


  2. #2
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    You need to manually trigger an end-of-file indication on stdin when you run the program (after supplying all the input you intend to be counted). The way you do that depends on your operating system, but definitely requires action by you (the user).

    If you don't do that, getchar() will never return the value EOF, so the while loop will never terminate, and the printf() statements will not be reached.
    Right 98% of the time, and don't care about the other 3%.

  3. #3
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    Thank you very much! I found that control+d

  4. #4
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    Or you could just replace the EOF with
    Code:
    while ((c = getchar()) != '0')
    and the program should stop with the loop.

  5. #5
    Code Goddess Prelude's Avatar
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    Quote Originally Posted by Dakshin View Post
    Or you could just replace the EOF with
    Code:
    while ((c = getchar()) != '0')
    and the program should stop with the loop.
    It'll certainly stop the loop, but given that the loop should accept any character and not just digits, your suggestion breaks the algorithm.
    My best code is written with the delete key.

  6. #6
    young grasshopper jwroblewski44's Avatar
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    Try creating a text file that contains your input. Then run the program like: ./foo < sample.txt, or "cat sample.txt | ./foo"
    amadeus111 likes this.

  7. #7
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    Quote Originally Posted by Prelude View Post
    It'll certainly stop the loop, but given that the loop should accept any character and not just digits, your suggestion breaks the algorithm.
    I don`t see why... the 0 is in quotes, isn`t it? The program is checking a character, not integer
    It's a miracle that curiosity survives formal education - Albert Einstein

  8. #8
    young grasshopper jwroblewski44's Avatar
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    The program is checking a character, not integer
    Exactly. The program should be able to accept a '0' as acceptable input, not to stop the loop.

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