cut of first char of a string

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

Replies are listed 'Best First'.
Re: cut of first char of a string by Corion (Patriarch) on Mar 08, 2005 at 08:17 UTC
In addition to the solutions mentioned at Chop command that removes the first character (of which I find the name `chip` especially cute), I found another solution, which is really contorted but does the thing: `perl -pe "$_ = join '', splice @{[split //]}, 1"` [download]	[reply] [d/l]
Re^2: cut off first char of a string by Happy-the-monk (Canon) on Mar 08, 2005 at 14:37 UTC
of which I find the name `chip` especially cute I like `chimp` for the counterpart of `chomp` even better =) Cheers, Sören	[reply]
Re: cut of first char of a string by sh1tn (Priest) on Mar 08, 2005 at 08:20 UTC
`$_ = '12345'; $_ = join '',(split/^./);` [download]	[reply] [d/l]
Re^2: cut of first char of a string by holli (Abbot) on Mar 08, 2005 at 08:33 UTC
Very nice++. I really like this one. holli, /regexed monk/	[reply] [d/l]
Re: cut of first char of a string by davido (Cardinal) on Mar 08, 2005 at 08:19 UTC
Is there any kind of sanity check to pass? If not... `# One way... $s = join '', ( split //, $s )[ 1 .. length($s) - 1 ]; print $s, $/;` [download] Update: And another..... `$s = pack 'A', unpack( 'xA', $s ); # ASCII only, please ;) print $s, $/;` [download] Dave	[reply] [d/l] [select]
Re^2: cut of first char of a string by bart (Canon) on Mar 08, 2005 at 10:00 UTC
`$s = pack 'A', unpack( 'xA', $s ); # ASCII only, please ;)` I see no reason for the pack. And you're better of using `'a'` not `'A'`, unless you really want to trim trailing spaces. `$s = unpack 'xa*', "qwerty "; print "'$s'\n";` [download]	[reply] [d/l] [select]
Re: cut of first char of a string by bart (Canon) on Mar 08, 2005 at 10:13 UTC
More split silliness. `(undef, $s) = split //, $s, 2;` [download] The 3rd parameter `2` makes split split into only 2 parts. I then simply ignore the first part.	[reply] [d/l]
Re^2: cut of first char of a string by Anonymous Monk on Mar 08, 2005 at 10:29 UTC
Note that your solution makes $s undefined if $s was equal to the empty string. `chop` doesn't undef an empty string.	[reply]
Re: cut of first char of a string by borisz (Canon) on Mar 08, 2005 at 08:38 UTC
`$s = unpack "xA", $s; $s = substr($s, 1); substr($s, 0, 1, "");` [download] Update:* remove wrong $s = in the last substr thanks to nothingmuch. Boris	[reply] [d/l]
Re^2: cut of first char of a string by nothingmuch (Priest) on Mar 14, 2005 at 00:33 UTC
In the last one didn't you mean without `$s =`? -nuffin zz zZ Z Z #!perl	[reply] [d/l]
Re: cut of first char of a string by chb (Deacon) on Mar 08, 2005 at 10:27 UTC
This uses a core module (and is Sick And Twisted(TM)): `use strict; use warnings; use Math::BigInt; my $s = 'Hello World'; $s = reverse ((Math::BigInt->new('0b' . (unpack('B', $s) & ('00000000' . ('11111111' x (length($s) - 1))))))->as_bin()) +; $s =~ s!b0!!; $s = reverse(pack('b', $s)); print "'", $s, "'\n";` [download]	[reply] [d/l]
Re: cut of first char of a string by ambrus (Abbot) on Mar 08, 2005 at 12:08 UTC
There are an infinity of ways of course, but here are some. `substr($s, 0, 1, ""); substr($s, 0, 1) x= 0; $s =~ /.(.)/s and $s = $1; open $s, "<", \$s; seek $s, 1, 0; local $/; $s = <$s>; # using no _add +ittional_ vars $s = substr $s, 1; $s = substr $s, 1, ~0>>1, "JAPH"; $s=~s s.sss;` [download] Update 2006 apr 11.* Here is a list of other threads on choping the first character of strings; thanks to Limbic~Region for finding them. howto strip the first char of a string? Deleting from front of string First char out of a string & surprises with errors on chop reverse $string (that doesn't work!) Chopping the beginning of a string? and this thread, cut of first char of a string If so many people want this, maybe we really need the chip/chimp functions in perl6? Also, on `substr($s, 0, 1) x= 0;`, see substr() as an lvalue.	[reply] [d/l] [select]
Re^2: cut of first char of a string by MidLifeXis (Monsignor) on Mar 08, 2005 at 17:58 UTC
I especially like the last one (six 's's. Hmm, would that be six-σ?). Very cool. --MidLifeXis	[reply]
Re: cut off first char of a string by Roy Johnson (Monsignor) on Mar 08, 2005 at 12:08 UTC
I haven't seen these posted yet: `($_) = /.(.)/s; # or $_ = substr($_, -length($_)+1); # or /./s and $_ = $';` [download] Caution:* Contents may have been coded under pressure.	[reply] [d/l]
Re: cut of first char of a string by rinceWind (Monsignor) on Mar 08, 2005 at 12:37 UTC
There's a whole aspect of this question which nobody has touched on yet. I'm talking about the precise meaning of "first char". Consider the situation when $s is a utf-8 string. The first "character" could be several bytes long. This means that the regexp and chop methods will work on full "characters", but substr operates on "bytes". I attended a talk recently at london.pm on this subject, the slides of which are here. -- I'm Not Just Another Perl Hacker	[reply]
Re^2: cut of first char of a string by demerphq (Chancellor) on Mar 08, 2005 at 13:42 UTC
This means that the regexp and chop methods will work on full "characters", but substr operates on "bytes". AFAIK unless the use bytes pragma is in effect substr operates on characters, not on bytes. Maybe the behaviour you describe is true pre 5.8.x but it isnt true in 5.8: `D:\Development>perl5.8.5 -le "my $str='ba'.pack('U',0x0370).'!'; print +f qq'$_ : %d\n', ord(substr($str,$_,1)) for 0..length($str)-1" 0 : 98 1 : 97 2 : 880 3 : 33 D:\Development>perl5.8.5 -Mbytes -le "my $str='ba'.pack('U',0x0370).'! +'; printf qq'$_ : %d\n', ord(substr($str,$_,1)) for 0..length($str)-1 +" 0 : 98 1 : 97 2 : 205 3 : 176 4 : 33` [download] --- demerphq	[reply] [d/l]
Re: cut of first char of a string by Limbic~Region (Chancellor) on Mar 08, 2005 at 13:50 UTC
holli, If we are just being silly: `$str = $_->[0] ? $str . $_->[1] : '' for map { [ $_, substr($str,$_,1) + ] } 0 .. length($str) - 1;` [download] Cheers - L~R	[reply] [d/l]
Re: cut of first char of a string by japhy (Canon) on Mar 08, 2005 at 15:31 UTC
What a shame we can't write functions and what-not. I'd say the best way is to write an XS module that increments the SV's IV value, sets the OOK flag, and decrements its CUR value: `% perl -MDevel::Peek $x = "japhy"; Dump($x); $x =~ s/\C//; Dump($x); __END__ SV = PV(0x814ce90) at 0x81603ac REFCNT = 1 FLAGS = (POK,pPOK) PV = 0x815d008 "japhy"\0 CUR = 5 LEN = 6 SV = PVIV(0x814d2a0) at 0x81603ac REFCNT = 1 FLAGS = (POK,OOK,pPOK) IV = 1 (OFFSET) PV = 0x815d009 ( "j" . ) "aphy"\0 CUR = 4 LEN = 5` [download] _____________________________________________________ Jeff `japhy` Pinyan, P.L., P.M., P.O.D, X.S.: Perl, regex, and `perl` hacker How can we ever be the sold short or the cheated, we who for every service have long ago been overpaid? ~~ Meister Eckhart	[reply] [d/l]
Re: cut of first char of a string by Anonymous Monk on Mar 08, 2005 at 08:51 UTC
Not necessary '^' metasym: `my $s = "123456789"; $s =~ s/.//` [download]	[reply] [d/l]
Re^2: cut of first char of a string by Corion (Patriarch) on Mar 08, 2005 at 08:55 UTC
This doesn't do 'the right thing' for strings starting with a newline (which admittedly is a border case): `perl -MData::Dumper -e "$foo=qq(\nHello);$foo =~ s/.//; print Dumper \ +$foo"` [download] Adding the `/s` flag makes dot match newline too: `perl -MData::Dumper -e "$foo=qq(\nHello);$foo =~ s/.//s; print Dumper +\$foo"` [download]	[reply] [d/l] [select]
Re: cut of first char of a string by TimToady (Parson) on Mar 10, 2005 at 08:41 UTC
Well, if you don't count `$_` as an extra variable because it's already implicitly there, you can do it like this: `use bytes; if (vec($s,3,2) < 3) { vec($s,$_,8) = vec($s,$_+1,8) for 0..length($s)-2; chop($s); } else { vec($s,$_,8) = vec($s,$_+1,8) for 0..length($s)-2; chop($s); while (vec($s,3,2) == 2) { vec($s,$_,8) = vec($s,$_+1,8) for 0..length($s)-2; chop($s); } }` [download] Update: Hmm, here's a solution without $_: `use bytes; if (vec($s,3,2) < 3) { () = $s =~ m/.(?=.)(?{ vec($s,pos($s)-1,8) = vec($s,pos($s),8) +})/sg; chop($s); } else { () = $s =~ m/.(?=.)(?{ vec($s,pos($s)-1,8) = vec($s,pos($s),8) +})/sg; chop($s); while (vec($s,3,2) == 2) { () = $s =~ m/.(?=.)(?{ vec($s,pos($s)-1,8) = vec($s,pos($s +),8)})/sg; chop($s); } }` [download]	[reply] [d/l] [select]
Re: cut of first char of a string by cog (Parson) on Mar 08, 2005 at 10:42 UTC
Actually, this: `$s =~ s/^.//; print "$s\n";` [download] Could be written as: `$s =~ s/.//; print "$s\n";` [download] Update: I had assumed the string would only contain the regular \w characters; won't work for strings starting with \n, obviously (because the dot doesn't match newlines). See Re: cut of first char of a string.	[reply] [d/l] [select]
Re: cut of first char of a string by jbrugger (Parson) on Mar 08, 2005 at 09:46 UTC
`#!/bin/perl use strict; my $s = "Hello world!"; print substr($s,1,length($s));` [download]	[reply] [d/l]
Re: cut of first char of a string by Anonymous Monk on Mar 08, 2005 at 10:25 UTC
Some variations on four themes: `substr($s, 0, 1, "")`, `$s =~ s/.//s;`, and use of `split` and `unpack`. $s = (split /./s, $s, 2)[1] err ""; # Needs 'defined-or' patch, or 5.9 +.1 $s = (split /./s, $s, 2)[1]; $s = "" unless defined $s; $s = length $s ? (split /./s, $s, 2)[1] : ""; $s = join "", map {substr $s, $_, 1} grep {$_} 0 .. length($s)-1; substr $s, $_, 1, $_ ? substr($s, $_, 1) : "" for 0 .. length($s)-1; local $a = 0; $s = join "", grep {$a++} split //, $s; local $" = ""; $s = "@{[(split //, $s)[1 .. length($s)-1]]} $s =~ s/(?<!.).//sg; local $a; $s =~ s/.(??{$a++ ? "(?!)" : "(?=)"})//sg; $s = pack "A", (unpack "A", $s)[1 .. length($s)-1]; $s = pack "A", unpack "xA", $s if length $s; $s = pack "A*", unpack "xA@{[length($s)-1]}", $s if length $s; [download]	[reply] [d/l] [select]
Re: cut of first char of a string by sh1tn (Priest) on Mar 08, 2005 at 12:24 UTC
First, but not last: `$_ = '12345';s/(.(.*))/$2or$1/e` [download]	[reply] [d/l]
Re^2: cut of first char of a string by Anonymous Monk on Mar 08, 2005 at 13:47 UTC
That doesn't work correctly: `perl -wle '$_ = '10'; s/(.(.*))/$2or$1/e; print' 10` [download]	[reply] [d/l]
Re^3: cut of first char of a string by sh1tn (Priest) on Mar 08, 2005 at 14:16 UTC
Yes, that doesn't, but this does: `s/(.(.*))/($2ne'')?$2:$1/e` [download]	[reply] [d/l]
Re^4: cut of first char of a string by Anonymous Monk on Mar 08, 2005 at 15:08 UTC
Re^5: cut of first char of a string by sh1tn (Priest) on Mar 08, 2005 at 15:27 UTC
Re: cut of first char of a string by blazar (Canon) on Mar 08, 2005 at 13:10 UTC
How many ways How many ways does Perl have to cut off the first char of a string? At a first glance it seems that this has not been mentioned yet, although basically it may be thought of as a variation of several of those that have been: `$ perl -lne 'print for /(.)(.*)/' dfdfsdgdfs d fdfsdgdfs stgsghttsthe s tgsghttsthe` [download]	[reply] [d/l]
Re: cut of first char of a string by eisforian (Novice) on Mar 08, 2005 at 15:31 UTC
Silly and convoluted: `$s = "12345678"; $s = join '', ( split //, $s )[ ( sprintf( '%03d%03d', length($s), length($s) ) / 7 / 11 / 13 - sprintf( '%03d', length($s) ) + 1 ) .. length($s) - 1 ]; print "$s\n";` [download]	[reply] [d/l]
Re: cut of first char of a string by Joost (Canon) on Mar 08, 2005 at 15:58 UTC
`use Symbol; my $s = "123456789"; Symbol::qualify_to_ref"s::".reverse$s&"\0".("\xff"x length$s); $s=reverse keys %s::;` [download] "What should it profit a man, if he should win a flame war, yet lose his cool?"	[reply] [d/l]
Re: cut of first char of a string by Jasper (Chaplain) on Mar 08, 2005 at 15:46 UTC
`$_ = $' x /./` edit: damn, I see Roy already had this (effectively)	[reply] [d/l]
Re: cut of first char of a string by calin (Deacon) on Mar 08, 2005 at 16:57 UTC
This does not exactly meet your requirements (no additional vars), but since everybody is going for crazy solutions and I have time to kill, here it is: `use v5.8; $s = "abcdef"; # or initialize it yourself ($s, $_) = (undef, $s); $s.=???!??:$&while/./g; print "$s\n";` [download] Warning: Does not work correctly under Perls earlier than 5.8 (change in semantics). It can be fixed though, at the expense of aesthetics.	[reply] [d/l]
Re: cut of first char of a string by Anonymous Monk on Mar 08, 2005 at 17:17 UTC
How many ways does Perl have to cut off the first char of a string? An infinite number, of course. For example, there are an infinite number of variations of the following solution: Append a string known not to be within the string, move the first character after the unique tag, then remove everything after the unique tag. You can increase the length of the unique tag string towards infinity, and you'll get an infinite number of solutions. -- Ytrew	[reply]
Re^2: cut of first char of a string by sh1tn (Priest) on Mar 09, 2005 at 00:56 UTC
`$_ = '12345';$_ = join'',(@{[split//]}[1..@{[split//]}]) # ?` [download]	[reply] [d/l]
Re: cut of first char of a string by Whitehawke (Pilgrim) on Mar 12, 2005 at 05:56 UTC
Well, here's a couple of simple ones: `print join'',@{[do{shift@{$s=[split//,$s='foobarbaz']};@$s}]} print $s=reverse@{$s=do{pop @{$s=[split//,reverse$s='foobarbaz']};$s}}` [download] Although, I'm honestly not sure why the `$s=` that immediately precedes the `do` is necessary in the second one. Can anyone explain it to me?	[reply] [d/l] [select]
Re^2: cut of first char of a string by ambrus (Abbot) on Jul 04, 2005 at 08:47 UTC
I'm not sure but I think it's needed because you assign an anonymous array to `$s` before it, so if you do not set `$s`, the rightmost `$s` will give that array.	[reply] [d/l] [select]
Re: cut of first char of a string by sh1tn (Priest) on Mar 10, 2005 at 06:43 UTC
`$_='0123456789' ;s;.(?=(.+));$1;s&&s;(.+)(\1);$1;s;` [download]	[reply] [d/l]


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