Load file: __search.sml

   This module searches a stream for a string by using a simple brute force
   algorithm.  It demonstrates the use of the TextIO structure, in particular
   the underlying functional streams used in the TextIO.StreamIO structure.
 
   The module provides three functions: Search.searchInput, 
   Search.searchStream, and Search.searchFile, which search standard
   input, the specified stream, and the specified file respectively.

   For example

      Search.searchInput ();

   gives
 
      Enter string to search through:
      The quick brown fox . . .              [typed by user]
      Enter string to search for:
      brown                                  [typed by user]
      String found at:
      brown fox . . .

   while

      Search.searchFile("foo","fox");

   returns true if the string 'fox' is found in file `foo', raising 
   exception Io if the file is not found, and Search.searchStream takes
   a string and a stream and searches for the first in the second.