http://www.perlmonks.org?node_id=199684


in reply to Perl Humor

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

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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");

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How do I convert a number to a string?

Use sprintf: 

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

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How can I tell if a string is a number?

The simplest method is: 

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

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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";
  }

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

Edit kudra, 2002-09-21 Fixed literal brackets

Replies are listed 'Best First'.
Re^2: Perl Humor
by Aristotle (Chancellor) on Sep 21, 2002 at 09:06 UTC
    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.

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