Re: Number Guess

I remember doing this game when I was first learning in BASIC. And then the corrolary - you pick the number, the computer guesses it. I learned binary searches that day, without realising it. ;-)

Comments:

use strict; use warnings; Always. Unless you know what you're doing.
Formatting. There are two major styles of braces. I'd suggest picking one. Although there can be religious wars on the topic of which one, and I have my preference as well, I'm not going to offer more advice than "just pick one".
Indentation. Whitespace is your friend. Make blocks of code easier to follow by lining up the left indent approprately.
Next is the use of goto. Although it has some uses, most of them are for advanced users only. As in, only once you've mastered not using goto can you give a reasonable justification for using it. At least, that's my opinion on using goto. In this case, you're using it to somewhat emulate a while loop. So just use a while loop, and people (like me) won't complain. To this end, I'd put the game itself into a "game" subroutine, and then be able to just wrap the call to the game sub in a small while loop.
Generally speaking, a single line of output is represented by a single print statement. Exceptions to this, unlike the exceptions to goto, are commonplace, however, so don't take this as a hard-and-fast rule or anything. For example, instead of
```
    print "Sorry, you ran out of guesses.  My number was ";
    print $value;
    print ". \n";
[download]
```
use
```
    print "Sorry, you ran out of guesses.  My number was ", $value, ".
+\n";
[download]
```
Some people will use perl's interpolation to do this as:
```
    print "Sorry, you ran out of guesses.  My number was $value.\n";
[download]
```
The former may be faster, but in reality the deciding factor should be what you find to be more readable.
Comments ... should go before what they're commenting, not after. Code is not a suspense novel - you shouldn't need to wait to see what really is happening. Code should be extremely boring where the plot is revealed before anything happens.

With all that in mind, here's your code with all of these changes. If you have any questions, don't hesitate to ask.

#Guessing Game
#You only get 10 tries!
#Gives the option of starting over.
#This version should count your turns for you, down from ten.

use strict;
use warnings;

#This is how many guesses you get.
my $max_guesses = 10;

sub game
{
    #This is the number they have to guess: a random integer.
    my $value = int(rand(200));

    print "Pick a number between 0 and 200.\n";

    for (my $tries = $max_guesses; $tries; --$tries) {
        print "You have ", $tries, " guesses left.\n";
        my $guess = <STDIN>;
        if($guess>$value) {
            print "You need to guess a lower number.\n";
            print "Guesses left: ", $tries, "\n";
        } elsif($guess<$value) {
            print "You need to guess a higher number.\n";
            print "Guesses left: ", $tries, "\n";
        } else {
            print "You guessed my number in ", 
                $max_guesses - $tries,
                " guesses.  Thanks for playing. \n";
            return;
        }
    }

    print "Sorry, you ran out of guesses.  My number was ", $value, ".
+\n";
}

my $again = 'y';
while ($again eq 'y')
{
    game();
    print "Play Again? (y/n) \n";

    $again = <STDIN>;
    chomp ($again);
}
print "Goodbye!\n";
[download]

Comment on Re: Number Guess Select or Download Code

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Re^2: Number Guess by cryptoquip (Novice) on Jul 15, 2005 at 19:33 UTC
Wow, truly the monks are wise and patient. Thanks for the great advice. Yes, I had some sense that `goto` might be a little hacky, but I didn't know how to use subroutines. Obviously, they are the magic answer I needed. Also, I did `use strict` and `use warnings` while I was working on this, but after I knew it would work, I didn't bother pasting them in here--why? Who knows; however, I now see the error of my ways. Looking at your `for` loop, I have a question. How does this handle the situation in which the player does successfully guess the answer in under ten tries? Since you have set the loop to run ten times, it looks like it will print "you have x guesses left" and wait for guess input even after you have won the game. I have just run the code and seen that this is not the case, but I can't figure out why. (Also, it looks like the "guesses left" line needs to be removed from the `if` statements, since you have put it at the top of the `for` loop. But this is a simple matter.) Here is another question: why do I have to `chomp $again`, but not `chomp $guess`?	[reply] [d/l] [select]
Re^3: Number Guess by Tanktalus (Canon) on Jul 15, 2005 at 20:41 UTC
Question 1: guessing the answer in under 10 tries. The statement you missed is "return". It causes the subroutine to return to whoever called it immediately. All loops that it may be in at that point are automatically exited directly to the caller, bypassing any and all other statements in the subroutine. Question 2: chomping. Your $guess is a number. Perl's DWIMery trick with numbers is to treat anything that looks like a number as a number. So if you have a string such as "12afsd4583", perl will treat it as the number 12. e.g., `$ perl -e 'print 0+"12afsd4583";print $/' 12` [download] In your case, the string $guess really is "123\n". Perl sees the "123" part as a number, and then it sees stuff that isn't numeric and cuts it off at that point. So it will do an implicit 'chomp'-like action. However, with $again, you're comparing it with the eq operator. Perl can't know, based on string context, whether the \n is important or not, so you have to be explicit. Another way to avoid the chomp is to use a less-precise match, such as a regular expression, e.g., `$again =~ /y/i` will match anything with a 'y' or a 'Y' in the string, whether it's followed by a carriage return or not. BTW - I pointed out the strict comment because while I was rewriting your code (or, rather, mostly just reformatting), I came upon a problem that would have been caught sooner had strict been used. Not a problem in your code, but in an intermediate code between what you had and what I ended up with. ;-) Another advantage of using strict when it's not necessarily needed: adding features and refactoring become easier. Or at least safer. ;-)	[reply] [d/l] [select]
Re: Number guess by cryptoquip (Novice) on Jul 15, 2005 at 21:55 UTC
Thanks for your help!	[reply]
Re^2: Number Guess by cryptoquip (Novice) on Aug 05, 2005 at 18:51 UTC
Just for kicks, here's my corrolary, where the computer guesses. It turned out a lot simpler. I'm trying harder to make it pretty, too. #The computer will try to guess your number. #Watch out! It knows if you're cheating. use strict; use warnings; sub game{ my $min=0; my $max=200; my $guess; my $response="h"; print "Think of a number between $min and $max, and I will guess wha +t it is. Type h if your number is higher than my guess, and type l i +f it is lower. Type = if I have guessed your number.\n"; while ($response ne "="){ if ((($max-$min)/2)<1){ print "You're not playing fair! I quit.\n"; return; } else{ $guess=int($max-(($max-$min)/2)); print "My guess is ",$guess,".\n"; $response = <STDIN>; chomp($response); if ($response eq "h"){ $min=$guess; } elsif ($response eq "l"){ $max=$guess; } } } } my $again = 'y'; while ($again eq 'y'){ game(); print "That was fun--no really, it was. Play again? (y/n) \n"; $again = <STDIN>; chomp ($again); } print "Goodbye!\n"; [download]	[reply] [d/l]