Truth table printer

  Hi all,

this mail is just to share a little program 'ttable' that prints the
truth table of a logical expression using the perl operators plus <=>
(equivalence) and => (implication). For example:

  >> ttable "((A=>B)&&(B=>C)) => (A=>C)"
 
        A B C  |  ((A=>B)&&(B=>C)) => (A=>C)
        ------------------------------------
        0 0 0  |  1
        0 0 1  |  1
        0 1 0  |  1
        0 1 1  |  1
        1 0 0  |  1
        1 0 1  |  1
        1 1 0  |  1
        1 1 1  |  1

  At the heart, there is the code that is not optimized in any way.

    $_ = 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,\"\\n\"","}"x@v, "\n";
    print "\n";

How much more concise could it be, beyond removing needless spaces?

The main problem is that the <=> and => operators have higher
precedence than the not operator !. Any cool ideas to change that?

  Cheers,

  Etienne

PS : I attach the whole script, with pod included (it prints its own
     documentation when run w/out argument).


-- 
Etienne Grossmann ------ http://www.cs.uky.edu/~etienne

#!/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,\"\\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>[email protected]<gt>

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

=cut