Feb 2, 2012

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 %s\n",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 = '\0';
  return tokentype = BRACKETS;
 else if (isalpha(c)) {
  for(*p++ = c; isalnum(c = getch());)
   *p++ = c;
  *p = '\0';
  return tokentype = NAME;
 } else
  return tokentype = c;

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