Re: Perl Humor

[gmpassos]

The best is this 3 questinos, making fun with C and ROMAN Numbers:

------------------------------------------
How do I convert a string to a number?

Use this atoi function:

  sub atoi {
    my $t;
    foreach my $d (split(//, shift())) {
      $t = $t * 10 + $d;
    }
  }
  $number = atoi("123");

------------------------------------------
How do I convert a number to a string?

Use sprintf:

  $string = sprintf("%f", 123.45);

------------------------------------------
How can I tell if a string is a number?

The simplest method is:

   if ($string == "$string") { 
   # It is a number
   }

Note the use of the == operator to compare the string to its numeric value. However, this approach is dangerous because the $string might contain arbitrary code such as @{[system "rm -rf /"]} which would be executed as a result of the interpolation process. For safety, use this regular expression:

  if ($var =~ /(?=.)M{0,3}(C[MD]|D?C{0,3})(X[CL]|L?X{0,3})(I[XV]|V?I{0
+,3})/) {
    print "$var contains a number.\b";
  }

Graciliano M. P.
"The creativity is the expression of the liberty".

Edit kudra, 2002-09-21 Fixed literal brackets

[Aristotle]

the $string might contain arbitrary code such as @{[system "rm -rf /"]} which would be executed as a result of the interpolation process.

Heh, that's mocking shell, not C, and really caught me off guard for a moment before the d'uh bells went off.

Makeshifts last the longest.

[blakem]

The authors of Advanced Perl Programming were caught off guard by this one as well. See Trojan Horse? (taint mode)

-Blake