in reply to Resetting variables

By jove, I think I got it...

Firstly, although I am not certain, I believe the error message is erroneously pointing to the wrong line $guess !~ m/[[:alpha:]]/ rather the error occurs in the elsif portion, where you have 

$guess =~ /[$good_guesses]/

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During the 1st pass, $good_guesses is either undefined, or set to a single letter (or multiple letter? doesn't matter).

On second pass, the $good_guesses is reset to a null string. 

$guess =~ /[$good_guesses]/

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gets translates to ... 
$guess =~ /[]/

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However, if I am not mistaken, character classes will accept a ']' as a valid element of the character class, if it is the first element of the class. So, the parser is taking the ']' as an element of the class, and then continues to look for the closing square bracket.

For whatever reason, if $good_guesses is undefined, the parser figures it out the way you meant. (UPDATE: Nope, that's not the reason, see update below)

To get your code to work, I re-initialized $good_guesses = undef; in your "reset_game" sub.

PS: I wrote my response after I got your program to work, but I did not actually go and read up on all the particulars of character classes in regular expressions, so I may not be entirely accurate.

Sandy

PS (again) ... That was fun!

UPDATE: Made mistake... the reason the code works when $good_guesses is undefined is that there is a condition in front of the condition... 

elsif ((defined($good_guesses))&&($guess =~ /[$good_guesses]/))

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that prevents the interpretation 
$guess =~ /[]/

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when $good_guesses is not defined

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Re^2: Resetting variables
by yacoubean (Scribe) on Dec 21, 2004 at 21:36 UTC
    Hmm, I believe I am checking to make sure $good_guesses is defined (unless I don't understand what defined() really does): 
    } elsif ((defined($good_guesses))&&($guess =~ /[$good_guesses]/)) {
        print "\n***You already guessed that letter!*** (hit any key)\
+n"; <>;
    } else {
        if ($word =~ /[$guess]/) {
            if (defined($good_guesses)) {
                $good_guesses .= "$guess" unless ($guess =~ /[$good_gu
+esses]/);
            } else {
                $good_guesses .= "$guess";
            }

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[d/l]
      Simply put... 
      my $var;     # variable is undefined
if ($var) { ... }  # $var is false because it is undefined
if (defined $var) {...}  # false

$var = "";
if ($var) { ... } # false because $var is null string
if (defined $var) {...} # true because $var has been
                        # defined as having a null string

$var = 0;
if ($var) { ... } # false because $var is zero
if (defined $var) {...} # true because $var has been
                        # defined as zero

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[d/l]
Re^2: Resetting variables
by yacoubean (Scribe) on Dec 21, 2004 at 22:04 UTC
    Yes, you appear to be right Sandy! I comment out two chunks that are doing stuff with $good_guesses, and it works (well, not the way I want, but I don't get the error). Now I have to figure out how to fix that, because it is now doing it on every run, not just the second pass. I don't know why though, because I'm defining $good_guesses = "" at the top.

    A lot of folks have wagged fingers at me for using global variables, and I know what they mean. I just don't know how else to do it! If I want to have a variable that needs to be accessed/updated by the main loop and by multiple subs...how can you do that without storing the variable outside of all the subs? If I try to put it in the loop it will be zeroed out on every loop, and the same with the subs. Any ideas would be appreciated.

    This is what I mean:

    Read more... (378 Bytes)
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[d/l]
      Oops, our posts have crossed in the mail (so to speak).

      Try either 

      if ($goodguesses && ($whatever =~ /[$goodguesses]/) {...}

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      or undefine $goodguesses 
      $goodguesses = undef;

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      see previous post (just before your last one, for the differences between 'false' and 'defined'

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[d/l]
[select]
        AAAhhhh!! You set me straight. ;) Using your clarifications, It now works on the first and second passes! Thanks a bunch.
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