Feb 1, 2012

K & R C Programs Exercise 5-11.

K and R C, Solution to Exercise 5-11:
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 the entab and detab(written as exercises in chapter 1) to accept a list of tab stops as arguments. Use the default tab settings if there are no arguments. Read more about C Programming Language .

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#include<stdio.h>
#define MAXLINE 100
#define TABINC 8
#define YES 1
#define NO 0
void settab(int argc , char *argv[], char *tab);
void entab(char *tab);
void detab(char *tab);
int tabpos(int pos, char *tab);

main(int argc, char *argv[])
{
 char tab[MAXLINE + 1];
 settab(argc, argv, tab);
 entab(tab);
 settab(argc, argv, tab);
 detab(tab);
 return 0;
}

/*entab: replace strings of blanks with tabs and blanks */
void entab(char *tab)
{
 int c, pos;
 int nb = 0;
 int nt = 0;
 for(pos = 1;(c=getchar()) != EOF;pos++)

  if(c == ' '){
   if(tabpos(pos, tab) == NO)
    ++nb;
   else{
    nb = 0;
    ++nt;
   }
  }else {
   for(;nt > 0;nt--)
    putchar('\t'); 
   if (c == '\t')
    nb = 0;
   else
    for(;nb > 0;nb--)
     putchar(' ');
   putchar(c);
   if(c == '\n')
    pos = 0;
   else if(c == '\t')
    while (tabpos(pos(pos, tab) != YES)
      ++pos;
  }
}

/*detab:replace tab with blanks*/
void detab(char *tab)
{
 int c,pos = 1;
 while ((c = getchar()) != EOF)
  if (c == '\t') {
   do
    putchar(' ');
   while (tabpos(pos++, tab) != YES);
  }else if(c == '\n'){
   putchar(c);
   pos = 1;
  }else{
   putchar(c);
   ++pos;
  }
}


//setab: set tab stops in array tab
void settab(int argc, char *argv[], char *tab)
{
 int i, pos;
 if (argc <= 1)
  for(i = 1; i <= MAXLINE; i++)
   if(i % TABINC == 0)
    tab[i] = YES;
   else tab[i] = NO;
 else{
  for(i = 1;i <= MAXLINE; i++)
   tab[i] = NO;
  while(--argc > 0){
   pos = atoi(*++argv);
   if(pos > 0 && pos <= MAXLINE)
    tab[pos] = YES;
  }
 }
}


//tabpos: determine if pos is at a tab stop
int tabpos(int pos, char *tab)
{
 if (pos > MAXLINE)
  return YES;
 else
  return tab[pos];
}

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