Chop command that removes the first character

mosh has asked for the wisdom of the Perl Monks concerning the following question:

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Re: Chop command that removes the first character by BrowserUk (Patriarch) on Oct 26, 2004 at 07:52 UTC
I have one in my utils library called `chip` which seems appropriate. sub chip{ substr $_[ 0 ], 0, 1, '' } my $s = 'the quick brown fox jumps over the lazy dog'; print chip( $s ), ' : ', $s while $s; t : he quick brown fox jumps over the lazy dog h : e quick brown fox jumps over the lazy dog e : quick brown fox jumps over the lazy dog : quick brown fox jumps over the lazy dog q : uick brown fox jumps over the lazy dog u : ick brown fox jumps over the lazy dog i : ck brown fox jumps over the lazy dog c : k brown fox jumps over the lazy dog k : brown fox jumps over the lazy dog : brown fox jumps over the lazy dog b : rown fox jumps over the lazy dog r : own fox jumps over the lazy dog o : wn fox jumps over the lazy dog w : n fox jumps over the lazy dog n : fox jumps over the lazy dog : fox jumps over the lazy dog f : ox jumps over the lazy dog o : x jumps over the lazy dog x : jumps over the lazy dog : jumps over the lazy dog j : umps over the lazy dog u : mps over the lazy dog m : ps over the lazy dog p : s over the lazy dog s : over the lazy dog : over the lazy dog o : ver the lazy dog v : er the lazy dog e : r the lazy dog r : the lazy dog : the lazy dog t : he lazy dog h : e lazy dog e : lazy dog : lazy dog l : azy dog a : zy dog z : y dog y : dog : dog d : og o : g g : [download] Examine what is said, not who speaks. "Efficiency is intelligent laziness." -David Dunham "Think for yourself!" - Abigail "Memory, processor, disk in that order on the hardware side. Algorithm, algorithm, algorithm on the code side." - tachyon	[reply] [d/l] [select]
Re^2: Chop command that removes the first character by tachyon (Chancellor) on Oct 26, 2004 at 10:08 UTC
To complete the theme: `sub chimp (@) { s!^$/+!! for @_ }`	[reply] [d/l]
Re^3: Chop command that removes the first character by BrowserUk (Patriarch) on Oct 26, 2004 at 10:26 UTC
Ooh! Ooh! Ooh! :) Examine what is said, not who speaks. "Efficiency is intelligent laziness." -David Dunham "Think for yourself!" - Abigail "Memory, processor, disk in that order on the hardware side. Algorithm, algorithm, algorithm on the code side." - tachyon	[reply]
Re^3: Chop command that removes the first character by Anonymous Monk on Oct 26, 2004 at 14:51 UTC
`sub chimp (@) {s!^$/+!! for (@_ ? @_ : $_)}` [download]	[reply] [d/l]
Re^4: Chop command that removes the first character by tachyon (Chancellor) on Oct 27, 2004 at 02:16 UTC
Re^3: Chop command that removes the first character by ihb (Deacon) on Mar 10, 2005 at 12:49 UTC
`chomp()` does not remove all trailing record separators, just one. The special case is paragraph mode where all trailing newlines are removed. When in fixed-length record mode (`$/ = \$some_int`) or slurp mode (`$/ = undef`) `chomp()` does nothing. All these special cases aren't handled by `&chimp`. Also, the return value isn't analoguous with `chomp()`'s. `ihb` See perltoc if you don't know which perldoc to read!	[reply] [d/l] [select]
Re: Chop command that removes the first character by Corion (Patriarch) on Oct 26, 2004 at 07:40 UTC
The naive approach of `perl -le "$f='hello world'; chop reverse $f; print $f"` [download] doesn't work sadly, and the correct approach of `perl -le "$f='hello world'; $f=reverse $f;chop $f;$f=reverse $f; print + $f"` [download] is far too clumsy, so relying on the fact that `substr` returns an lvalue, I'd use: `perl -le "$f='hello world'; substr($f,0,1)=''; print $f"` [download] Of course, there are many many more methods of removing the first character of a string: `perl -le "$f='hello world'; $f=~s!^.!!; print $f"` [download] or `perl -le "$f='hello world'; $f=~s!.!!; print $f"` [download] which I guess is the shortest variant, clocking in at 9 characters.	[reply] [d/l] [select]
Re^2: Chop command that removes the first character by ikegami (Patriarch) on Jan 15, 2007 at 23:44 UTC
`perl -le "$f='hello world'; $f=~s!^.!!; print $f" perl -le "$f='hello world'; $f=~s!.!!; print $f"` [download] should be `perl -le "$f='hello world'; $f=~s!^.!!s; print $f" perl -le "$f='hello world'; $f=~s!.!!;s print $f"` [download] The first character could be a newline.	[reply] [d/l] [select]
Re: Chop command that removes the first character by insaniac (Friar) on Oct 26, 2004 at 07:46 UTC
a simple regex will help you, the beauty of perl :-D `$_="monkey" ; s/^.(.*)$/$1/; print` [download] hope this helps.. -- to ask a question is a moment of shame to remain ignorant is a lifelong shame	[reply] [d/l]
Re^2: Chop command that removes the first character by tachyon (Chancellor) on Oct 26, 2004 at 10:36 UTC
Actually you want `s/^.//s` You need the /s to make a . match anything - it does not by default. Also why capture to $1 only to replace it with an exact replica?	[reply] [d/l]
Re^3: Chop command that removes the first character by insaniac (Friar) on Oct 26, 2004 at 12:35 UTC
i don't know... i'm just a beginner, beginners make mistakes :-D so i'm sorry: i just assumed the first character would never be a newline (that's the only thing the `/s` does actually.. it allows you to also match a newline with the `.`) -- to ask a question is a moment of shame to remain ignorant is a lifelong shame	[reply] [d/l] [select]
Re: Chop command that removes the first character by mosh (Scribe) on Oct 26, 2004 at 08:37 UTC
Thanks all. btw, I meant chomp of course...	[reply]
Re^2: Chop command that removes the first character by Happy-the-monk (Canon) on Oct 26, 2004 at 09:47 UTC
I meant chomp of course Then you will have to test whether the first character has the value of Perl's special variable `$/` to be removed. See `chomp`. Cheers, Sören	[reply]
Re: Chop command that removes the first character by TedPride (Priest) on Oct 26, 2004 at 07:52 UTC
EDIT: I was thinking chomp, my bad. The only real possibility is the following, then: `$varname = substr($varname, 1);` [download]	[reply] [d/l]
Re^2: Chop command that removes the first character by mawe (Hermit) on Oct 26, 2004 at 08:03 UTC
Hi! Chop removes only whitespace... What you mean is chomp. chop removes any character. EDIT: TedPride: Please don't just delete what you wrote. Now nobody knows what I have been talking about ... as usual :) mawe	[reply]
Re^3: Chop command that removes the first character by tachyon (Chancellor) on Oct 26, 2004 at 09:56 UTC
Because you have quoted it we know what was there. As a minor pedant chomp will remove any char that corresponds to $/ aka the $INPUT_RECORD_SEPARATOR. For example if you undef $/ but don't localise (or restore) it chomp will mysteriously fail. Not only that it is a global..... cheers tachyon	[reply]
Re: Chop command that removes the first character by TedPride (Priest) on Oct 26, 2004 at 13:35 UTC
Well then, my original solution works: `$textvar =~ s/^\s+//;` [download] I use this one a lot.	[reply] [d/l]


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