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

/**
 *  atoi: convert s to integer
 *  Based closely on version 2 from K&R 2nd.
 */ 
int 
atoi (char s[]) 
{
  int i, n, sign;

  // Skip over whitespace
  for (i = 0; isspace (s[i]); i++) 
    ; // The body of this is empty

/*
  Could also have been
  i = 0;
  while (isspace (s[i]))
    i++;
 */

  // Determine the sign
  sign = (s[i] == '-') ? -1 : 1; 

/* 
  Shorthand for
  if (s[i] == '-')
    sign = -1;
  else
    sign = 1;
 */

  // Skip over the sign
  if (s[i] == '+' || s[i] == '-') 
    i++; 

  // Do the real work
  for (n = 0; isdigit(s[i]); i++)
    n = 10 * n + (s[i] - '0'); 
/*
  Look at each digit in the string.
    s[i] is a character
    i++ is stepping through those characters
    isdigit checks whether it's a digit
  How is n behaving?
 */

  // And we're done
  return sign * n;
} // atoi

int 
main (int argc, char *argv[])
{
  int i = atoi (argv[1]);
  printf ("%d squared is %d.\n", i, i*i);
  return 0;
} // main