[FWP] A "Cheating" hangman dealer

[Rich Morin <rdm@cfcl.com>]

I recently attended a talk by Damian Conway on his Quantum:Superpositions
module.  At the risk of getting things totally wrong, I will hand-wave a
brief explanation, because the notions are critical to my FWP topic.  I
will then say a bit about the "hangman" game and present my FWP challenge.

Quantum::Superpositions
-----------------------

The motivation and basis for the module comes from quantum mechanics, in
which entities can simultaneously be in different states, until they are
actually observed.  Think "probability clouds", "wave/particle duality",
and "Schro:dinger's cat", as examples.

The QS module defines a set of operators ("any", "all", and "eigenstates")
which allow the programmer to deal with sets of "superposed" values as if
they were scalars.  If, for instance, I said "$a = any(1,3,5,7,9);", $a
would have the capability of being any or all of the initial values,
depending on the context.  I could then say things such as:

   print "$a\n";			# print a value, at random
   if ($a > 4) ...		# true; some values qualify
   if ($a < 0) ...		# false; no values qualify

You will need more background than this to actively participate in the
challenge, but this is a reasonable starting point for reading along.
If you want to play (or simply read Damian's notes), pick up his QS
module (Quantum-Superpositions-1.03) from the CPAN:

   NAME
     Quantum::Superpositions - QM-like superpositions for Perl

   DESCRIPTION
     The Quantum::Superpositions module provides a new scalar data
     structure: the superposition.  In a metaphor drawn from quantum
     mechanics, superpositions store a collection of values by overlaying
     them in parallel superimposed states within a single scalar
     variable.  Which allows for cool stuff like:

         use Quantum::Superpositions;
         if ($x == any($a, $b, $c) { ...  }
         while ($nextval < all(@thresholds) { ... }
         $max = any(@value) < all(@values);

Hangman
-------

In the "hangman" game, the "dealer" presents the "player" with a set
of character spaces to be filled in.  In each "move", the player offers
a letter.  If the letter matches any of the spaces in the dealer's word,
the dealer fills in those spaces with the letter.  If the letter fails to
match anything in the word, the dealer draws another element (e.g., head,
neck) on a stick-figure representation of a "hanged" person.  Eventually,
either the player succeeds in determining the word, or an entire body has
been drawn.  See hangman(6) for an example implementation:

   NAME
        hangman - the game of hangman

   SYNOPSIS
        /usr/games/hangman

   DESCRIPTION
        In hangman, the computer picks a word from the on-line
        word list and you must try to guess it.  The computer
        keeps track of  which letters have been guessed and how
        many wrong guesses you have made on the screen in a
        graphic fashion.

   FILES
        /usr/share/dict/words    On-line word list

   AUTHOR
        Ken Arnold

Cheating in Hangman
-------------------

I don't really know if it qualifies as cheating, but I have found
that it spices up the "dealer" role quite a bit to leave the word
initially undefined, save for the number of characters it contains.
So, for example, I might draw six character positions and wait for
the player to pick a letter.  S/he chooses "e", so I draw the head
and eliminate all "e"-containing words from my candidate list.

As the game continues, my options get more and more limited; at
some point, unless the player runs out of moves, I will find that
I can no longer reject the player's letter (i.e., all of the words
that are left in my list have the proposed letter).  I must then
pick a set of positions and fill them in with the letter.

In general, I will have come down to a single word at this point,
but this is not really a requirement.  If, for instance, I have:

   r _ _ _ _ _

the word could be any six-character word that starts with an "r" and
doesn't contain any of the previously eliminated letters.  Of course,
if the player has already tried [a-gi-ln-qsu-xz], my set may contain
only the word "rhythm".

The Challenge
-------------

Create a "cheating hangman dealer", in Perl.  This could be done in
a variety of ways, but I would like to see at least some solutions
that use QS, in order to see how the program's design changes.

The goal is to create something elegant and comprehensible, BTW, so
leave the white space in (:-).  Also, I hope to write up this topic
in my UnixInsider (http://www.unixinsider.com) column, "Silicon Carny",
so please don't post any trade secrets or other IP you care about.

FWIW, I have downloaded the QP module, but haven't actually started
playing with it.  I hope to have my own entries in the challenge, but
I will be just as happy to look at (and steal from :-) others' work...

-r
-- 
--
http://www.cfcl.com/rdm
email: rdm@cfcl.com
phone: +1 650-873-7841

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