Just another perl hacker: Difference between revisions
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imported>Aleksander Stos m (Perl example 3 moved to Just another perl hacker: This has more 'universal' meaning, independent of our content) |
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Example: | Example: | ||
<code>$ perl -e 'print grep(s/^\d+(.*)/$1 /, sort(split(/ /,"8hacker, 4Perl 1Just 2another")));'</code> | <code>$ perl -e 'print grep(s/^\d+(.*)/$1 /, sort(split(/ /,"8hacker, 4Perl 1Just 2another")));'</code> | ||
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</code> | </code> | ||
Yep. "just another perl hacker". Just don't ask why ... | Yep. "just another perl hacker". Just don't ask why ...[[Category:Suggestion Bot Tag]] |
Latest revision as of 07:00, 7 September 2024
![](http://s9.addthis.com/button1-share.gif)
Example:
$ perl -e 'print grep(s/^\d+(.*)/$1 /, sort(split(/ /,"8hacker, 4Perl 1Just 2another")));'
Result:
Just another Perl hacker,
Perl is evaluated from inside to outside of parens and from right to left, so ist is possible to squeeze all steps into a one-liner like the one above. But the example will be much more understandable if it is expanded into a program using intermediate variables:
$string = "8hacker, 4Perl 1Just 2another";
## split $string on white space (/ / is a shortcut with special meaning in context of `split')
@list = split(/ /,$string); # resulting in $list[0] = '8hacker,', list[1] = '4Perl', etc.
## the leading numbers are for the benefit of the builtin sort directive
@sorted = sort (@list); # resulting in $sorted[0] = '1Just', $sorted[0] = '2another', etc.
## the following pattern detects a leading (shortcut '^') digit (shortcut \d, the '+' means at least one)
## and caches ('capture' shortcut '()') the remainder ('all characters' shortcut '.*')
$pattern = '^\d+(.*)';
## the example uses the builtin 'grep' and we could be done right here:
@result1 = grep(s/^\d+(.*)/$1 /, @sorted);
## but for a step-by-step explanation we will convert the grep into an equivalent loop:
@result2 = (); ## initialize to empty list, actually the default
@index = (0 .. $#sorted); ## ($#sorted: shortcut for index of last element of '@sorted')
foreach $index (@index) ## ($index and @index are two independent variables!)
{
## to 'use =~ s///' directly on $sorted[$index]
## would change the element, so we use a temp variable
$tmp = $sorted[$index];
$tmp =~ s/$pattern/$1/; ## e.g. substitute '4Perl' with 'Perl'
$result2[$index] = $tmp;
}
## a 'print @list' automatically inserts the output field separator ('$,')
print "result1:",@result1,"\n";
print "result2:",@result2,"\n";
Voila:
result1:Just another Perl hacker,
result2:Just another Perl hacker,
But what do you think is the output of this 2003 beauty from perlmonks.org?
$ perl -e '
not exp log srand xor s qq qx xor
s x x length uc ord and print chr
ord for qw q join use sub tied qx
xor eval xor print qq q q xor int
eval lc q m cos and print chr ord
for qw y abs ne open tied hex exp
ref y m xor scalar srand print qq
q q xor int eval lc qq y sqrt cos
and print chr ord for qw x printf
each return local x y or print qq
s s and eval q s undef or oct xor
time xor ref print chr int ord lc
foreach qw y hex alarm chdir kill
exec return y s gt sin sort split
'
Yep. "just another perl hacker". Just don't ask why ...