macOS keytab problem

[jamesapp]

confused about a program from a book on c programming. Got the following error messages from the K + R book, when i tried to compile the program.

james-collinss-macbook-pro:chap5 jamescollins$ gcc keytab.c -o keytab.out
keytab.c:8: warning: ‘struct key’ declared inside parameter list
keytab.c:8: warning: its scope is only this definition or declaration, which is probably not what you want
keytab.c:15: error: ‘NKEYS’ undeclared here (not in a function)
keytab.c:17: error: redefinition of ‘struct key’
keytab.c: In function ‘main’:
keytab.c:43: warning: passing argument 2 of ‘binsearch’ from incompatible pointer type
keytab.c: At top level:
keytab.c:54: error: conflicting types for ‘binsearch’
keytab.c:8: error: previous declaration of ‘binsearch’ was here

the program is supposed to count occurences of C keywords
the book gives a list of words, and says to initialize the list as an external variable.

here is my source file which i called keytab.c:

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

#define MAXWORD 100

int geword(char *, int);
int binsearch(char *, struct key *, int);

struct key {
    char *word;
    int count;
};

struct key keytab[NKEYS];

struct key {
    char *word;
    int count;
 } keytab[] = {
    "auto", 0,
    "break", 0,
    "case", 0,
    "char", 0,
    "const", 0,
    "continue", 0,
    "default", 0,
    /* ... */
    "unsigned", 0,
    "void", 0,
    "volatile", 0,
    "while", 0,
};

/* count C keywords */
main()
{
  int n;
  char word[MAXWORD];
  
  while (getword(word, MAXWORD) != EOF)
      if (isalpha(word[0]))
          if ((n = binsearch(word, keytab, NKEYS)) >= 0)
              keytab[n].count++;
  for (n = 0; n < NKEYS; n++)
       if (keytab[n].count > 0)
           printf("%4d %s\n",
                keytab[n].count, keytab[n].word);
  return 0;
}

/* binsearch: find word in tab[0]...tab[n-1] */
int binsearch(char *word, struct key tab[], int n)
{
  int cond;
  int low, high, mid;
  
  low = 0;
  high = n - 1;
  while (low <= high) {
      mid = (low+high) / 2;
      if ((cond = strcmp(word, tab[mid].word)) < 0)
          high = mid - 1;
      else if (cond > 0)
           low = mid + 1;
      else
           return mid;
  }
  return -1;
}

/* getword: get next word or character from input */
int getword(char *word, int lim)
{
  int c, getch(void);
  void ungetch(int);
  char *w = word;
  
  while (isspace(c = getch()))
      ;
  if (c != EOF)
      *w++ = c;
  if (!isalpha(c)) {
      *w = '\0';
      return c;
  }
  for ( ; --lim > 0; w++)
      if (!isalnum(*w = getch())) {
          ungetch(*w);
          break;
      }
  *w = '\0';
  return word[0];
}

/* getch and ungetch */
#define BUFSIZE 100

char buf[BUFSIZE];  /* buffer for ungetch */
int bufp = 0;  /* next free position in buf */

int getch(void)  /* get a (possibly pushed back) character */
{
  return (bufp > 0) ? buf[--bufp] : getchar();
}

void ungetch(int c)  /* push character back on input */
{
  if (bufp >= BUFSIZE)
      printf("ungetch: too many characters\n");
  else
      buf[bufp++] = c;
}

 

[primes]

Many things wrong...

Try...

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

#define MAXWORD 100
#define NKEYS 11


struct key {
    char *word;
    int count;
 } keytab[NKEYS] = {
    "auto", 0,
    "break", 0,
    "case", 0,
    "char", 0,
    "const", 0,
    "continue", 0,
    "default", 0,
    "unsigned", 0,
    "void", 0,
    "volatile", 0,
    "while", 0
};

int geword(char *, int);
int binsearch(char *, struct key *, int);

/* count C keywords */
main()
{
  int n;
  char word[MAXWORD];
  
  while (getword(word, MAXWORD) != EOF)
      if (isalpha(word[0]))
          if ((n = binsearch(word, keytab, NKEYS)) >= 0)
              keytab[n].count++;
  for (n = 0; n < NKEYS; n++)
       if (keytab[n].count > 0)
           printf("%4d %s\n",
                keytab[n].count, keytab[n].word);
  return 0;
}

/* binsearch: find word in tab[0]...tab[n-1] */
int binsearch(char *word, struct key tab[], int n)
{
  int cond;
  int low, high, mid;
  
  low = 0;
  high = n - 1;
  while (low <= high) {
      mid = (low+high) / 2;
      if ((cond = strcmp(word, tab[mid].word)) < 0)
          high = mid - 1;
      else if (cond > 0)
           low = mid + 1;
      else
           return mid;
  }
  return -1;
}

/* getword: get next word or character from input */
int getword(char *word, int lim)
{
  int c, getch(void);
  void ungetch(int);
  char *w = word;
  
  while (isspace(c = getch()))
      ;
  if (c != EOF)
      *w++ = c;
  if (!isalpha(c)) {
      *w = '\0';
      return c;
  }
  for ( ; --lim > 0; w++)
      if (!isalnum(*w = getch())) {
          ungetch(*w);
          break;
      }
  *w = '\0';
  return word[0];
}

/* getch and ungetch */
#define BUFSIZE 100

char buf[BUFSIZE];  /* buffer for ungetch */
int bufp = 0;  /* next free position in buf */

int getch(void)  /* get a (possibly pushed back) character */
{
  return (bufp > 0) ? buf[--bufp] : getchar();
}

void ungetch(int c)  /* push character back on input */
{
  if (bufp >= BUFSIZE)
      printf("ungetch: too many characters\n");
  else
      buf[bufp++] = c;
}

Boiled down to:

1. Declarations out of order (or un-needed).
2. No declaration for NKEYS (you must define it first).

Now to complete it, you must add extra "keywords" into your table and make the NKEYS constant match the number of keywords.

I saved this as "count.c" on my system, then started up TERMINAL in same directory (sorry, I am a UNIX person), then ran "cc count.c".

To test, I ran "./a.out <count.c". I ran the program against itself and it seems to work except that the rest of the C-lang keywords need to be added in.

 

[primes]

I forgot...

Also, you left a trailing comma in the array def and the list of keyword MUST appear in ascending, lexicographic order (!) or the binsearch may not work correctly.

 

[jamesapp]

thanks