[edflsafoiewq]

I think most of us who really like it read it as kids which colors it too much. I distinctly remember this proof that you can't solve the MU-puzzle as the first piece of mathematics I ever saw. In one swoop I discovered impossibility proofs, invariants, and the use of divisibility which suffused the whole book with an aura of initiation into great mysteries that it will never attain for the already-initiated.

[justinator]

I read it in art school (swiped from my then-girlfriend's bookshelf), and it was nice to have a connection between my school of art weirdos and putting myself through the same school by teaching myself software engineering. I distinctly remembering writing a Perl script to highlight that the Mu puzzle is unsolvable.

    #!/usr/bin/perl -w
    use strict; 


    my %tried = (); 

    main(); 

    sub main { 

        my @rules = (
                     \&rule_one, 
                     \&rule_two,
                     \&rule_three, 
                     \&rule_four,
                    ); 

        my $axiom = 'MI';
    
        my @path; 
        my @tries; 

         solve($axiom, \@rules); 
    }


    sub solve { 

        my @app; 


        my ($axiom, $rules) = @_; 
        my $i = 0; 

        foreach(@$rules){ 
            my $tmp =  $_->($axiom);
            push(@app, $tmp) if $tmp;
        }

        foreach(@app){ 

            next if $tried{$_};
            next unless (length($_) < 1000); 
    
            print $_ . "\n";
    
            $tried{$_} = 1; 
    
            if($_ eq 'MU'){ 
                print "YES!\n\n\n"; 
                exit;
            }
            solve($_, $rules); 
        }

    }



    sub rule_one { 
        # If any string ends in I, you can append U

        my $str = shift; 

        if ($str =~ m/I$/){ 
            return $str . 'U';     
        }else{ 
            return undef; 
        }
    }




    sub rule_two { 
        # If any string begins with M, 
        # you can duplicate the string after M,    

        my $str = shift; 

        if($str =~ /^M/){ 
            return 'M' . substr($str, 1) . substr($str, 1); 
        }else{ 
            return undef;
        }
    }




    sub rule_three { 
        # If any string contains III, 
        # you can replace the III with U

        my $str = shift; 
        if($str =~ /III/){ 
            $str =~ s/III/U/g;
            return $str; 
        }else{ 
            return undef;     
        }
    }




    sub rule_four { 
        #If any string contains UU, 
        # you can delete the UU

        my $str = shift; 

        if($str =~ /UU/){ 
            $str =~ s/UU//g; 
            return $str;
        }else{ 
            return undef; 
        }
    }