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K and R C, Solution to Exercise 6-5:
K and R C Programs Exercises provides the solution to all the exercises in the C Programming Language (2nd Edition). You can learn and solve K&R C Programs Exercise.
Write a function undef that will remove a name and definition from the table maintained by lookup and install. Read more about C Programming Language .

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* programs for commercial purposes,
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int undef(char * name) {
 struct nlist * np1, * np2;

 if ((np1 = lookup(name)) == NULL)  /*  name not found  */
  return 1;

 for ( np1 = np2 = hashtab[hash(name)]; np1 != NULL;
   np2 = np1, np1 = np1->next ) {
  if ( strcmp(name, np1->name) == 0 ) {  /*  name found  */

   /*  Remove node from list  */

   if ( np1 == np2 )
    hashtab[hash(name)] = np1->next;
   else
    np2->next = np1->next;

   /*  Free memory  */

   free(np1->name);
   free(np1->defn);
   free(np1);

   return 0;
  }
 }

 return 1;  /*  name not found  */
}

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/***********************************************************
* You can use all the programs on www.c-program-example.com
* for personal and learning purposes. For permissions to use the
* programs for commercial purposes,
* contact info@c-program-example.com
* To find more C programs, do visit www.c-program-example.com
* and browse!
*
* Happy Coding
***********************************************************/

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

#define MAXWORD 100
#define NDISTINCT 1000

struct tnode(
char *word;
int count;
struct tnode *addtree(struct tnode *, char *);
int getword(char *, int);
void sortlist(void);
void treestore(struct tnode *);
struct tnode *list[DISTINCT];
int ntn = 0;

/* print distinct words sorted in decreasing order of freq.*/
main()
{
struct tnode *root;
char word[MAXWORD]
int i;

root = NULL;
while(getword(word, MAXWORD) != EOF)
if(isalpha(word[0]))
root = addtree(root, word);
treestore(root);
sortlist();
for(i = 0;i < ntn; i++)
printf("%2d:%20sn",list[i]->count,list[i]->word);
return 0;
}

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

C Program Examples

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K & R C Programs Exercise 6-5.

K & R C Programs Exercise 6-4.