2 basic questions

[Anonymous Monk]

Hello Monks,

I am pretty new to Perl. Kindly answer me if any of you can... :)

I have 2 questions today,

Question #1:

$check = "a";
$check++;
print $check;
exit;

This will give me answer as "b", but what should i do to get "d" or "e" (I mean to pass over 3 or 4 alphabets).

---

Question #2:

I have a string which have 2 alphabets, I need to trim it to 1 alphabet, ie, I only want the right alphabet, the left one should be trimmed out.

Example

 $input= "ab";
 $output = "b";

The alphabets can be any, not just "ab", it can be "cd" or "sp", In that case output should be "d" & "p" resp.

Thank you, Monks.

[tobyink]

use v5.12;

my $check = "a";
$check++ for 1..3;  # three letters
say $check;

$check++ for 1..24;  # another 24 letters, but there's only 26 in the 
+alphabet,
say $check;          # so what happens now we've run off the end?

# hmmm... that's handy.
# it takes us to the next part of your question...

my $input = $check;
my $output = substr($input, 1, 1); # skip one character, take one char
+acter

say $output;

[Anonymous Monk]

Thx Toby

[choroba]

1. The string increment is magical, but no other string operations are. Therefore, if you do not want to resort to ord arithmetics, you have to repeat the increment:

   my $check = 'a';
   $check++ for 1 .. 5;
   

2. TIMTOWTDI. You can for example use substr:

   my $check = 'cd';
   substr $check, 0, 1, q();
   

   Or, use a substitution:

   my $check = 'sp';
   $check =~ s/^.//;
   

[toolic]

For 1 you can use a for loop, for 2 you can use substr

use warnings;
use strict;

my $check = "a";
$check++ for 1..3;
print $check;
print "\n";

my $input= "ab";
print substr $input, -1, 1;
print "\n";

__END__

d
b

[Anonymous Monk]

thx Monk...

[ww]

Very basic and better answered for yourself by reading perldoc perlintro (from your command line)... and -- as is often the case -- correctly answered in many different ways. Here is a (partial) answer for each question:

my $check = "A";
for (1..2) {
    $check++;
}
say $check;

#2:

my $input = "xy";
$input = reverse ($input);
chop $input;
say $input;

The first, obviously, is a simplied loop using the range operator (alternate syntax is shown by other replies above); the second takes advantage of the otherwise little-used chop. Note that it will "work" even if your charpair is NOT an ordered pair.

Please take these for examples, and set yourself the task of finding at least two other ways to answer each of your questions.

[Anonymous Monk]

Thank you...

[karlgoethebier]

Another TIMTOWTDI:

my $result = (split "", "ab")[(length(qq(ab))-1)];

print $result;

Please note: with subtraction ;-)

Update:

Two more...

$result = pop @{ [ split( "", "ab" ) ] };

print qq($result\n);

$result = splice( @{ [ split( "", "ab" ) ] }, -1 );

print qq($result\n);

Perhaps this is the reason why some folks hate perl?

Regards, Karl

P.S.:

• length
• splice
• pop

[Anonymous Monk]

read perlintro and you'll know the answer, don't rely on magic increment or chr and ord, use "substitution" or transliteration operator

[Random_Walk]

Just playing, may not work in your character set:

perl -le "while(1){$a=$a?$a:ord'a';print chr$a;$a=++$a%ord'{';sleep 1}
+"

This probably will though

perl -le "$_='x';while(1){s/aa/a/;print$_++;sleep 1}"

Cheers,
R.