Try this

$s = "this is an\b correct usage";
$s =~ s[.\cH][]g;
print $s;

this is a correct usage
[download]

Update: Antirice is right, clumbsy.

$s = "My first attempt was slightly\b\b\b\b\b\b\b\bvery buggy, maybe t
+hus\b\bis better?";

$s =~ s[[^\cH]\cH][]g while 1+index $s, chr(8);

print $s;

My first attempt was very buggy, maybe this better?
[download]

Small bug:

#!/usr/bin/perl -wl

$s = "this is an\b\b not correct usage";
$s =~ s[.\cH][]g;

print $s;

print "and one's still there" if grep { ord == ord"\b" } split //,$s;
__END__
output:
this is  not correct usage
and one's still there
[download]

It looks correct at first glance, but the second backspace is still there.

Update: Much better. Only problem is in the case of a leading \b, you can get into an infinite loop. However only the regex needs alteration.

$s =~ s/(?:[^\cH]\cH|^\cH+)//g while ...
[download]

antirice    
The first rule of Perl club is - use Perl
The ith rule of Perl club is - follow rule i - 1 for i > 1

AWESOME, it sinks in slowly ;-)

This solves the problem from the poster below...

$s = "\bthis is an\b correct\b\b\b usage\b";
do 1  while ($s =~ s/(?:[^\cH]\cH|^\cH+)//g);
[download]

tr/\b//d would probably be the most efficient form but s/\010//g will also do the job. What is with all the .\010 and while(1)'s in the replies?

$_ = "hello\b\b\b\b\b\b\hello\b\b";
tr/\b//d;
print length($_), $/, $_, $/;
__DATA__
10
hellohello
[download]

cheers

tachyon

s&&rsenoyhcatreve&&&s&n.+t&"$'$`$\"$\&"&ee&&y&srve&&d&&print

You miss the point or I do.

When you remove the \b, you also have to remove the character behind it over which it backspaced. In your example, the final output should be something like "hel".

---

Examine what is said, not who speaks.

"Efficiency is intelligent laziness." -David Dunham
"When I'm working on a problem, I never think about beauty. I think only how to solve the problem. But when I have finished, if the solution is not beautiful, I know it is wrong." -Richard Buckminster Fuller
If I understand your problem, I can solve it! Of course, the same can be said for you.

If you don't have two backspaces in a row, this quick and dirty will do it:

$_ = "this is an\b correct usage";
s/.[\b]//g;
print;
[download]

Note that \b is a word boundary within a regex but a backspace within a character class.

For a more correct solution, see the Unix col command or col for PPT. See also Removing characters.

Make sense, if only you could tell the regex engine to work left to right it would work...I can't assume the user wont hit a backspace twice...I dit it about 6 times typing this reply ;-)

Out of the mouths of dab'es ! Isn't this a 'sexeger' situation?

Maybe someone should check my results, 'cuz I can't believe that adding in the reverse's doesn't impact these timings more.   I added a different routine to the mix benchmarked by antirice:

sub badkcams {
  $a = reverse $s;
  $a =~ s[\cH[^\cH]|\cH$][]g  while  1+index $a, chr(8);
  reverse $a;
}
[download]

I then ran the benchmark again:

           Rate    smack     new1       uk badkcams
smack     191/s       --     -96%     -97%     -97%
new1     5063/s    2547%       --      -7%     -25%
uk       5469/s    2759%       8%       --     -19%
badkcams 6715/s    3411%      33%      23%       --
           Rate    smack     new1       uk badkcams
smack    42.4/s       --     -22%     -30%     -44%
new1     54.7/s      29%       --      -9%     -27%
uk       60.2/s      42%      10%       --     -20%
badkcams 75.3/s      78%      38%      25%       --

Am I reading this right?   It's faster?!?
(This is Perl 5.8.0 AS build 806 running on WinXP.)

{
  local $_ = "this is an\b correct usage";
  s/(.[\b])//;
  print "$_\n";
}
[download]

Have you even tried it?

The OP wants to match a backspace, not a backslash followed by a "b"...

/\b/ doesn't match a backspace, though, but a word boundary. You have to use it in a class to make it match.

  s/.[\b]//g;
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local $_ = "this is an\b\b\b correct\b\b\b\b\b\b\b\borrect usage";
s/(.[\b])//;
print $_;
[download]

No, you are replacing backslash followed by 'b' as shown below.

local $_ = "this \\b is an\b\b\b correct\b\b\b\b\b\b\b\borrect usage";
print "$_\n\n";
s/(.\\b)//g;
print $_;
[download]

/-\

Please note the correction to 'noaltr_subst' by antirice earlier today in Re: Re: Re: Re: Re: Re: should this backspace removal code be done better?.   It doesn't change the timings much, just the correctness.

A couple of thoughts. First, the 'substr' test code doesn't return the same results as the others.

I'm also not sure that it makes sense to remove a backspace at the beginning of the line? What would that mean?

I don't think that it makes too much sense to benchmark strings much beyond a 80 chars or so. Mostly we don't type lines much longer than that, and optimising for the occasional use is pretty pointless. Actually, optimising this whole thing is pretty pointless unless we are going to write programs that simulate a person typing including their typos and corrections:) Even the slowest version is way faster than (I) can type a line of input.

Finally, if the optimisation is just for fun, a way to while away a boring Sunday afternoon, here's a version that does pretty well on the short tests, but comes in second on the longer strings.

Read more... (5 kB)

---

Examine what is said, not who speaks.

"Efficiency is intelligent laziness." -David Dunham
"When I'm working on a problem, I never think about beauty. I think only how to solve the problem. But when I have finished, if the solution is not beautiful, I know it is wrong." -Richard Buckminster Fuller
If I understand your problem, I can solve it! Of course, the same can be said for you.