On Jan 29, Mallik said:
>Can anybody explain the functionality of eval in brief?
For starters, please read 'perldoc -f eval'. All Perl functions are
explained in detail in the standard documentation.
eval() has two forms. The first takes a string, and treats it as Perl
code. It compiles and executes it, returning whatever value is
appropriate. If there is a fatal error, it sets the $@ variable.
my $string = "make the vowels capitals";
my $from = "aeiou";
my $to = "AEIOU";
eval "\$string =~ tr/$from/$to/";
# now $string is mAkE thE vOwEls cApItAls
We had to use eval() here, because tr/// doesn't interpolate variables.
If we'd just done
$string =~ tr/$from/$to/;
we'd be changing $ to $, f to t, r to o, o to o, and m to o, and the
string would be "oake the vowels capitals".
The other form is eval { CODE }. This executes a block of code in a
fail-safe environment. If there are any fatal errors, the $@ is set, and
the block is exited. A common use for this is:
print "Give me a number: ";
chomp(my $n = <STDIN>);
my $result = eval { 100 / $n };
if ($@) { print "You tried dividing by zero.\n" }
Basically, if we didn't use eval { } here, the program would die if the
user entered the number 0.
--
Jeff "japhy" Pinyan [EMAIL PROTECTED] http://www.pobox.com/~japhy/
RPI Acacia brother #734 http://www.perlmonks.org/ http://www.cpan.org/
<stu> what does y/// stand for? <tenderpuss> why, yansliterate of course.
[ I'm looking for programming work. If you like my work, let me know. ]
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