#!/usr/bin/perl -w
exec "perldoc $0" unless @ARGV;
$_ = shift;
$, = " ";
s/([a-z]+)/\$$1/ig;
@a{/(\$\w+)/g} = 1;
@v = sort keys %a;
($t="@v  |  $_") =~ s/\$//g;
s/<=>/==/g;
s/=>/<=/g;
($l=$t) =~ s/./-/g;
print "\n\t$t\n\t$l\n";
eval join "",(map{"for $_ (0,1){"}@v),"print \"\\t@v  | \",((",$_,")?1:0),\"\\n\"","}"x@v, "\n";
print "\n";

=head1 ttable - Print truth table of a logical proposition

Prints the truth table of a logical proposition in which variable names
consist of any number of consecutive letters, true is 1, false is 0,
and operators are

  Not !     And &&    Or ||  

in that order of precedence. You may also use
 
  Then =>   Iff <=>

B<but their precedence is greater than that of "!" and they cannot be
chained>.

=head2 EXAMPLES

  >> ttable 'A && (B || A)'
 
        A B  |  A && (B || A)
        ---------------------
        0 0  |  0
        0 1  |  0
        1 0  |  1
        1 1  |  1
 
  >> ttable '(B && (B || A)) <=> B'
 
        A B  |  (B && (B || A)) <=> B
        -----------------------------
        0 0  |  1
        0 1  |  1
        1 0  |  1
        1 1  |  1
 
=head1 AUTHOR Etienne Grossmann E<lt>etienne@cs.uky.eduE<gt>

If you have never seen unreadable code, read this program's.

=cut