K & R C Programs Exercise 6-6.

K and R C, Solution to Exercise 6-6:
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.
C Program to implement a simple version of the #define processor(i.e , no arguments) suitable for use with C programs, based on the routines of this section, You may also find getch and ungetch helpful.Read more about C Programming Language .

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***********************************************************/

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

#define MAXWORD 100

struct nlist{
struct nlist *next;
char *name;
char *defn;
};
void error(int, char*);
int getch(void);
void getdef(void);
int getword(char *,int);
struct nlist *install(char *,char *);
struct nlist *lookup(char *);
void skipblanks(void);
void undef(char *);
void ungetch(int);
void ungets(char *);


//simple version of #define processor
main()
{
char w[MAXWORD];
struct nlist *p;
while(getword(w, MAXWORD) != EOF)
if(strcmp(w, "#") == 0)
getdef();
else if(!isalpha(w[0]))
printf("%s",w);
else if ((p == lookup(w)) == NULL)
printf("%s",w);
else
ungets(p->defn);
}

//getdef:get defination and install it
void getdef()
{
int c,i;
char def[MAXWORD], dir[MAXWORD], name[MAXWORD];
skipblanks();
if(!isalpha(getword(dir,MAXWORD)))
error(dir[0],"getdef:expecting a directve after #");
else if(strcmp(dir,"define") == 0) {
skipblanks();
if(!isalpha(getword(name, MAXWORD)))
error(name[0],"getdef:non alpha name expected"):
else{
skipblanks();
for(i = 0;i < MAXWORD-1; i++)
if((def[i] = getch()) == EOF || def[i] == 'n')
break;
def[i] = '';
if(i <= 0)
error('n',"getdef:non alpha in define");
else
install(name, def);
}
}else if(strcmp(dir,"undef") == 0) {
skipblanks();
if(!isalpha(getword(name, MAXWORD)))
error(name[0],"getdef:non alphain undef"):
else
undef(name);
}else
error(dir[0],"getdef:expecting a directive after #");
}

//undef:remove a name and defination from the table
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 */
}

//error:print error message and skip the rest of the line
void error(int c, char *s)
{
printf("error:%sn",s);
while(c != EOF && c != 'n')
c = getch();
}

//skipblanks:skip blan and tab characters
void skipblanks()
{
int c;
while((c = getch()) == ' ' ||c == 't')
;
ungetch(c);
}

/*ungets: push string back onto the input*/
void ungets(char s[])
{
int len=strlen(s);
void ungetch(int);
while (len >0)
ungetch(s[--len]);
}
/*note: modify the getword function to return
spaces so that the output resembles the input data.*/
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K & R C Programs Exercise 6-4.

K and R C, Solution to Exercise 6-4:
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 C Program that prints the distinct words in its input sorted into decreasing order of frequency of occurrence. Precede each word by its count. Read more about C Programming Language .

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* for personal and learning purposes. For permissions to use the
* programs for commercial purposes,
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* 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 = '';
return c;
}


//comment: skip over comment and return a character
int comment()
{
int c;
while((c = getch()) != EOF)
if(c == '*')
if((c = getch()) == '/')
break;
else
ungetch(c);
return c;
}

//TREESTORE:STORE IN LIST[] POINTERS TO TREE NODES

void treestore(struct tnode *p)
{
if(p != NULL) {
treestore(p->left);
if(ntn < NDISTINCT)
list[ntn++] = p;
treestore(p->right);
}
}

//sortlist: sort list of pointers to tree nodes
void sortlist()
{
int gap, i,j;
struct tnode *temp;

for(gap = ntn/2;gap > 0;gap /= 2)
for(i = gap; i < ntn;i++)
for(j = i - gap;j >= 0;j -= gap) {
if((list[j]->count) >= (list[j+gap]->count))
break;
temp = list[j];
list[j] = list[j+gap];
list[j+gap] = temp;
}
}
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K & R C Programs Exercise 6-3

K and R C, Solution to Exercise 6-3:
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.
C Program to Write a cross-referencer program that prints a list of all words in a document, and, for each word, a list of the line numbers on which it occurs. Remove noise words like “the”, “and,” and so on. Read more about C Programming Language .

/***********************************************************
* 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 [email protected]
* To find more C programs, do visit www.c-program-example.com
* and browse!
* Original URL: http://www.c-program-example.com/2012/02/k-r-c-programs-exercise-6-3.html
* GitHub URL: https://github.com/snadahalli/cprograms/blob/master/knrc/knrc6_3.c
***********************************************************/

/** Write a cross-referencer program that prints a list of all words in a
* document, and, for each word, a list of the line numbers on which it
* occurs. Remove noise words like "the", "and," and so on.
**/

#include
#include
#include
#include

char *dupstr(char *s) {
char *p = NULL;
if(s != NULL){
p = malloc(strlen(s) + 1);
if(p) {
strcpy(p, s);
}
}
return p;
}

int i_strcmp(const char *s, const char *t) {
int diff = 0;
char cs = 0;
char ct = 0;

while(diff == 0 && *s != '' && *t != '') {
cs = tolower((unsigned char)*s);
ct = tolower((unsigned char)*t);
if(cs < ct) {
diff = -1;
}
else if(cs > ct) {
diff = 1;
}
++s;
++t;
}

if(diff == 0 && *s != *t) {
if(*s == '') {
diff = -1;
}
else {
diff = 1;
}
}

return diff;
}

struct linelist {
struct linelist *next;
int line;
};

struct wordtree {
char *word;
struct linelist *firstline;
struct wordtree *left;
struct wordtree *right;
};

void printlist(struct linelist *list) {
if(list != NULL) {
printlist(list->next);
printf("%6d ", list->line);
}
}

void printtree(struct wordtree *node) {
if(node != NULL) {
printtree(node->left);
printf("%18s ", node->word);
printlist(node->firstline);
printf("n");
printtree(node->right);
}
}

struct linelist *addlink(int line) {
struct linelist *new = malloc(sizeof *new);
if(new != NULL) {
new->line = line;
new->next = NULL;
}
return new;
}

void deletelist(struct linelist *listnode) {
if(listnode != NULL) {
deletelist(listnode->next);
free(listnode);
}
}

void deleteword(struct wordtree **node) {
struct wordtree *temp = NULL;
if(node != NULL) {
if(*node != '') {
if((*node)->right != NULL) {
temp = *node;
deleteword(&temp->right);
}
if((*node)->left != NULL) {
temp = *node;
deleteword(&temp->left);
}
if((*node)->word != NULL) {
free((*node)->word);
}
if((*node)->firstline != NULL) {
deletelist((*node)->firstline);
}
free(*node);
*node = NULL;
}
}
}

struct wordtree *addword(struct wordtree **node, char *word, int line) {
struct wordtree *wordloc = NULL;
struct linelist *newline = NULL;
struct wordtree *temp = NULL;
int diff = 0;

if(node != NULL && word != NULL) {
if(NULL == *node) {
node = malloc(sizeof **node);
if(NULL != *node) {
(*node)->left = NULL;
(*node)->right = NULL;
(*node)->word = dupstr(word);
if((*node)->word != NULL) {
(*node)->firstline = addlink(line);
if((*node)->firstline != NULL) {
wordloc = *node;
}
}
}
}
else {
diff = i_strcmp((*node)->word, word);
if(0 == diff) {

newline = addlink(line);
if(newline != NULL) {
wordloc = *node;
newline->next = (*node)->firstline;
(*node)->firstline = newline;
}
}
else if(0 < diff) {
temp = *node;
wordloc = addword(&temp->left, word, line);
}
else {
temp = *node;
wordloc = addword(&temp->right, word, line);
}
}
}

if(wordloc == NULL) {
deleteword(node);
}

return wordloc;
}


char *char_in_string(char *s, int c) {
char *p = NULL;

/* if there's no data, we'll stop */
if(s != NULL) {
if(c != '') {
while(*s != '' && *s != c) {
++s;
}
if(*s == c) {
p = s;
}
}
}
return p;
}

char *tokenise(char **s, char *delims) {
char *p = NULL;
char *q = NULL;

if(s != NULL && *s != '' && delims != NULL) {
/* pass over leading delimiters */
while(NULL != char_in_string(delims, **s)) {
++*s;
}
if(**s != '') {
q = *s + 1;
p = *s;
while(*q != '' && NULL == char_in_string(delims, *q)) {
++q;
}

*s = q + (*q != '');
*q = '';
}
}

return p;
}

int NoiseWord(char *s)
{
int found = 0;
int giveup = 0;

char *list[] = {
"a",
"an",
"and",
"be",
"but",
"by",
"he",
"I",
"is",
"it",
"off",
"on",
"she",
"so",
"the",
"they",
"you"
};

int top = sizeof list / sizeof list[0] - 1;
int bottom = 0;
int guess = top / 2;

int diff = 0;

if(s != NULL) {
while(!found && !giveup) {
diff = i_strcmp(list[guess], s);
if(0 == diff) {
found = 1;
}
else if(0 < diff) {
top = guess - 1;
}
else {
bottom = guess + 1;
}
if(top < bottom) {
giveup = 1;
}
else {
guess = (top + bottom) / 2;
}
}
}

return found;
}

char *GetLine(char *s, int n, FILE *fp) {
int c = 0;
int done = 0;
char *p = s;

while(!done && --n > 0 && (c = getc(fp)) != EOF) {
if((*p++ = c) == 'n') {
done = 1;
}
}

*p = '';
if(EOF == c && p == s) {
p = NULL;
}
else {
p = s;
}
return p;
}

#define MAXLINE 8192

int main(void) {
static char buffer[MAXLINE] = {0};
char *s = NULL;
char *word = NULL;
int line = 0;
int giveup = 0;
struct wordtree *tree = NULL;

char *delims = " tnrafv!"%^&*()_=+{}[]\|/,.<>:;#~?";

while(!giveup && GetLine(buffer, sizeof buffer, stdin) != NULL) {
++line;
s = buffer;
while(!giveup && (word = tokenise(&s, delims)) != NULL) {
if(!NoiseWord(word)) {
if(NULL == addword(&tree, word, line)) {
printf("Error adding data into memory. Giving up.n");
giveup = 1;
}
}
}
}

if(!giveup) {
printf("%18s Line Numbersn", "Word");
printtree(tree);
}

deleteword(&tree);
return 0;
}
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K & R C Programs Exercise 6-1.

K and R C, Solution to Exercise 6-1:
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.
C Program to write a routine that properly handles underscores, string constants, comments, or preprocessor control lines.Read more about C Programming Language .

/***********************************************************
* 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 [email protected]
* To find more C programs, do visit www.c-program-example.com
* and browse!
*
* Happy Coding
***********************************************************/

#include<stdio.h>
#include<ctype.h>
//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 = '';
return c;
}

//comment: skip over comment and return a character
int comment()
{
int c;
while((c = getch()) != EOF)
if(c == '*')
if((c = getch()) == '/')
break;
else
ungetch(c);
return c;
}

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