K & R C Programs Exercise 5-19.

K and R C, Solution to Exercise 5-19:
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 modify(K & R C Programs Exercise 5-18.) undcl so that it does not add redundant parentheses to declarations. Read more about C Programming Language .

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#define MAXTOKEN 100

enum { YES, NO};

int gettoken(void);
int nexttoken(void);
extern int tokentype;
extern char token[MAXTOKEN];
char out[1000];
extern int prevtoken = NO;
//UNDCL:convert word description to declaration
int type;
char temp[MAXTOKEN];
while (gettoken() !=EOF) {
strcy(out, token);
while ((type = gettoken()) != 'n')
if(type == PARENS || type == BRACKETS)
strcat(out, token);
else if(type == '*') {
if((type = nexttoken()) == PARENS || type == BRACKETS)
sprintf(temp, "(*%s)", out);
sprintf(temp, "*%s", out);
strcpy(out, temp);

}else if(type == NAME){
sprintf(temp, "%s%s",token, out);
strcpy(out, temp);
printf("Invalid input at %sn",token);
return 0;

//nexttoken: get the next token and push it back
int nexttoken(void)
int type;
extern int prevtoken;
type = gettoken();
prevtoken = YES;
return type;

//get token:return next token
int gettoken(void)
int c, getch(void);
void ungetch(int);
char *p = token;
if(prevtoken == YES) {
prevtoken = NO;
return tokentype;
while((c = getch()) == ' ' || c == 't')
if(c == '('){
if ((c = getch()) == ')'){
return tokentype = PARENS;
return tokentype = '(';
else if(c == '['){
for(*p++ = c; (*p++ = getch()) != ']';)
*p = '';
return tokentype = BRACKETS;
else if (isalpha(c)) {
for(*p++ = c; isalnum(c = getch());)
*p++ = c;
*p = '';
return tokentype = NAME;
} else
return tokentype = c;

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