/**
 * numbers.c - A simple program for extracting the numbers from an input file.
 *    Each number is printed on a separate line.
 */

// +--------+----------------------------------------------------------
// | Design |
// +--------+

/*
  In essence, there are four possible "states" of the program.  We
  can be
    * outside of a number,
    * in the portion of a number before the decimal point,
    * at the decimal point,
    * after the decimal point, but still in the number.

  Our action at each character is therefore a simple decision based
  on the kind of character (digit, decimal, other) and the current
  state.
    * (outside,digit) => print; state = before
    * (outside,point) => ignore
    * (outside,other) => ignore
    * (before,digit) => print
    * (before,point) => state = decimal
    * (before,other) => "ended the number" print a newline; state=outside
    * (decimal,digit) => "there's something after the decimal point"
      print the decimal point; preinct the digit; state = after
    * (decimal,point) => "the decimal point was meaningless"; print newline;
      state=outside
    * (decimal,other) => "the decimal point was meaningless"; print newline;
      state=outside
    * (after,digit) => print
    * (after,point) => "ended the number" print a newline; state=outside
    * (after,other) => "ended the number" print a newline; state=outside
        
  We can represent the states with constants (as in the example in K&R)
  or as an enum (which Gnu Coding Guidelines suggest).

  We can determine the type of a character using isdigit.
 */


// +---------+---------------------------------------------------------
// | Headers |
// +---------+

#include <stdio.h>	// For printf, getchar, and such
#include <ctype.h>	// For isdigit()


// +-------+-----------------------------------------------------------
// | Types |
// +-------+

/**
 * The states of our program.
 */
enum state { OUTSIDE, BEFORE, DECIMAL, AFTER };


// +------+------------------------------------------------------------
// | Main |
// +------+

int
main ()
{
  int ch;               // The input character
  enum state state;    // The state of the program

  // Initially, we seem to be outside a number.
  state = OUTSIDE;

  // Repeatedly read a character and process.
  while ((ch = getchar ()) != EOF)
    {
      // Handle digits
      if (isdigit (ch))
        {
          // Update the state
          if (state == DECIMAL)
            {
              printf(".");
              state = AFTER;
            } // if (state == DECIMAL)
          else if (state == OUTSIDE)
            state = BEFORE;
          // Print the character
          printf("%c", ch);
        } // if it's a digit

      // Handle decimal points
      else if (ch == '.')
        {
          if (state == BEFORE)
            state = DECIMAL;
          else if (state != OUTSIDE)
            {
              state = OUTSIDE;
              printf ("\n");
            }
        } // if it's a decimal point

      // Handle everything else
      else
        {
          if (state != OUTSIDE)
            {
              state = OUTSIDE;
              printf ("\n");
            }
        } // everything else
    } // while

  // On the slight chance that we ended in the middle of a line, make
  // sure that we don't have a newline left to print
  if (state != OUTSIDE)
    printf ("\n");

  // And we're done
  return 0;
} // main