Backhanded^H^H^H^H^H^Hspaces

Question

On some terminals, pressing backspace generates the control code ^H to delete the previous character. This gave rise to a snarky idiom where edits are feigned for comedic effect:

Be nice to this fool^H^H^H^Hgentleman, he's visiting from corporate HQ.

Given a string with one or more ^H's, output the result of backspacing on each ^H. The input will use only printable characters (ASCII 32-126), and ^ will only appear as ^H. Backspaces will never happen on empty text.

You may not assume that the output environment supports control codes, in particular the backspace code \x08.

>> Horse^H^H^H^H^HCow
Cow

>> Be nice to this fool^H^H^H^Hgentleman, he's visiting from corporate HQ.
Be nice to this gentleman, he's visiting from corporate HQ.

>> 123^H45^H^H^H78^H
17

>> Digital Trauma^H^H^H^H^H^H^H^H^H^H^H^H^H^HMaria Tidal Tug^H^H^H^H^H^H^H^H^H^H^H^H^H^H^HDigital Trauma
Digital Trauma

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\$\begingroup\$ Is AAA^HB^H^H valid? \$\endgroup\$
– Nathan Merrill
Commented Jul 10, 2015 at 21:47 — Nathan Merrill, Commented Jul 10, 2015 at 21:47
\$\begingroup\$ @NathanMerrill Yes, and it results in A. \$\endgroup\$
– xnor
Commented Jul 10, 2015 at 21:54 — xnor, Commented Jul 10, 2015 at 21:54
\$\begingroup\$ I suspect retina would do well here. \$\endgroup\$
– Claudiu
Commented Jul 10, 2015 at 21:55 — Claudiu, Commented Jul 10, 2015 at 21:55
\$\begingroup\$ @Fatalize: "Backspaces will never happen on empty text." \$\endgroup\$
– Maltysen
Commented Jul 10, 2015 at 22:06 — Maltysen, Commented Jul 10, 2015 at 22:06
\$\begingroup\$ @Maria Tidal Tug comes back to haunt me \$\endgroup\$
– Digital Trauma
Commented Jul 10, 2015 at 23:18 — Digital Trauma, Commented Jul 10, 2015 at 23:18

caird coinheringaahin g · Accepted Answer · 2021-04-08 21:55:49Z

2

Jelly, 9 bytes

œṣ⁾^HṖ;¥/

Try it online!

Not a new approach, but the question was missing a Jelly answer

How it works

œṣ⁾^HṖ;¥/ - Main link. Takes a string S on the left
  ⁾^H     - Yield "^H"
œṣ        - Split on "^H"
       ¥/ - Reduce by the following:
     Ṗ    -   Remove the last character
      ;   -   And append the right argument

answered Apr 8, 2021 at 21:55

caird coinheringaahin g♦

50.3k11 gold badges128 silver badges354 bronze badges

\$\begingroup\$ ping me in an hour :P \$\endgroup\$
– Wezl
Commented Apr 8, 2021 at 22:14

Add a comment |

user · Accepted Answer · 2021-04-09 13:09:28Z

Vim, 38 35 bytes

Saved 3 bytes thanks to Leo!

qa:%s/\([^H]\|\^\@<!.\)\^H//g
@aq@a

Try it online!

See Razetime's answer for a shorter and smarter version of this.

qa:%s/\([^H]\|\^\@<!.\)\^H//g
@aq@a

qa                                     Start recording a macro a
  :%s/                                 Substitute in entire file
      \([^H]\|\^\@<!H\)                Regex for the character to be deleted
        [^H]                           A character that isn't H
            \|                         or
                    H                  an H
              \^\@<!                   that doesn't have a ^ before it
                       \^H             All of that followed by ^H
                          //           Replace with empty string
                            g          Global flag so it replaces multiple times
                                       Enter the command
@a                                     Recursively call macro a
  q                                    Stop recording
   @a                                  Run the macro
```

You need to pass V the -v flag in order to use verbose mode that turns <cr> into a carriage return Try it online! You could also directly insert a newline in the code instead Try it online! — Leo, Commented Apr 9, 2021 at 0:45

Kade · Accepted Answer · 2015-07-11 01:38:33Z

1

Python 2, 74 + 2 = 76 Bytes

I've tried a few approaches so far, this is the best I've been able to come up with so far.

n=input();o='';c=0
for l in n:d=l=='^';o=[o+l*(1-c),o[:-1]][d];c=d
print o

edited Jul 11, 2015 at 1:38

answered Jul 11, 2015 at 1:30

Kade

7,87324 silver badges53 bronze badges

4

\$\begingroup\$ Where are those 2 extra bytes coming from? \$\endgroup\$
– xnor
Commented Jul 11, 2015 at 9:17
\$\begingroup\$ @xnor input has to be surrounded by quotes for this to work. I forgot to put that in the post. \$\endgroup\$
– Kade
Commented Jul 11, 2015 at 13:42
1

\$\begingroup\$ I think the usual convention has been to allow string arguments to be taken in quotes for free, but I'm not totally sure. \$\endgroup\$
– xnor
Commented Jul 13, 2015 at 7:19

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xnor · Accepted Answer · 2015-07-14 21:42:48Z

1

Mumps, 84 Bytes

R Z S T="",Y=$L(Z,"^H") F I=1:1:Y{S T=T_$P(Z,"^H",I) S:I<Y T=$E(T,1,$L(T)-1)} W !,T

This could probably be made shorter as a function (1 byte I was able to save in quick testing) but I kinda like the one-liner aspect... :-)

The braces come from the Intersystems Cache flavour of Mumps which is what I'm most versed in.

edited Jul 14, 2015 at 21:42

xnor

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answered Jul 14, 2015 at 19:17

zmerch

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DeadChex · Accepted Answer · 2015-07-15 22:55:24Z

1

Java - 123 bytes

I personally like the g---1 part the best.

String f(char[] a){String b="";for(int g=-1;++g<a.length;b=(a[g++]=='^'?b.substring(0,b.length()-1):b+a[g---1]));return b;}

expanded (slightly):

  String f(char[] a) {
      String b = "";
      for (int g = -1;
           ++g < a.length;
           b = (a[g++]=='^' 
                ? b.substring(0, b.length() - 1) 
                : b + a[g---1])
      );
      return b;
  }

edited Jul 15, 2015 at 22:55

DeadChex

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answered Jul 10, 2015 at 22:50

Stretch Maniac

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Community · Accepted Answer · 2017-05-23 12:41:23Z

Batch - 138 bytes

@!! 2>nul||cmd/q/v/c%0 %1&&exit/b
set s=%1&for /F %%a in ('"prompt $H&echo on&for %%b in (1)do rem"')do set D=%%a
echo %s:^H=!D! !D!%

The first line is a way of saving a few bytes over the lengthy @echo off&setLocal enableDelayedExpansion (which turns echo off and enables the delayed expansion of variables, in case you were wondering). I explained it in Tips for Golfing in Batch.

The second line is a neat little trick to save the a backspace control character into a variable. It's pretty hacky, and I can't pretend to take credit for it. It's sort of explained here. Basically uses the prompt command to generate a backspace character and captures it in a variable - in this case !D!.

The final line then performs the simple string manipulation of - replace ^H with !D!<SPACE>!D!.

C:\>bsp.bat "testing^H^H^H test"
"test test"

Unfortunately it breaks with cases like "AAA^HB^H^H" - where it should produce "A", it instead produces "A"B. Which is somewhat confusing. I'll have to look into how Batch string manipulation works in some more depth.

~~C:\>bsp.bat "AAA^HB^H^H" "A"B~~

Thanks to to some helpful people over here - I now realize that I was only saving the backspace character (0x08), and so was only overwriting the characters. It now works with examples like the following:

C:\>bsp.bat "AAA^HB^H^H"
"A"

there's a shorter version: set s=%1&for /F %%a in ('prompt $H^&cmd /k^<nul')do set D=%%a — ScriptKidd, Commented Apr 3, 2020 at 5:31

Martin Ender · Accepted Answer · 2015-11-17 21:12:07Z

1

JavaScript, 60 bytes

b=n=>(v=n.search('^H'))>0?b(n.replace(n.slice(v-1,v+2),'')):n

Not as good as edc65's answer, but I wanted to try something that didn't use Regex.

edited Nov 17, 2015 at 21:12

Martin Ender

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answered Nov 17, 2015 at 19:26

Amechra

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F. Hauri - Give Up GitHub · Accepted Answer · 2015-11-17 22:16:33Z

bash, 50 bytes

while [ "$a" != "${a/?^H/}" ];do a=${a/?^H/};done

Sample:

a=$'Horse^H^H^H^H^HCow'
while [ "$a" != "${a/?^H/}" ];do a=${a/?^H/};done
echo $a
Cow

a="Be nice to this fool^H^H^H^Hgentleman, he's visiting from corporate HQ."
while [ "$a" != "${a/?^H/}" ];do a=${a/?^H/};done
echo $a
Be nice to this gentleman, he's visiting from corporate HQ.

This could work with real (binaries) backspaces as well:

a=$'Be nice to this fool\b\b\b\bgentleman, he'\'$'s visiting from corporate HQ.'
echo $a.. but:
Be nice to this gentleman, he's visiting from corporate HQ... but:
printf %q\\n "$a"
$'Be nice to this fool\b\b\b\bgentleman, he\'s visiting from corporate HQ.'

while [ "$a" != "${a/?$'\b'/}" ];do a=${a/?$'\b'/};done
printf %q\\n "$a"
Be\ nice\ to\ this\ gentleman\,\ he\'s\ visiting\ from\ corporate\ HQ.

Aaron · Accepted Answer · 2015-12-16 20:27:10Z

1

><>, 39 38 36 bytes

There was no ><> answer so I thought I'd add one.

i:0(?v:'^'=?\
     ~   ~~i/
;!?lr<ro

edited Dec 16, 2015 at 20:27

answered Nov 17, 2015 at 14:40

Aaron

3,8491 gold badge16 silver badges30 bronze badges

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ProgramFOX · Accepted Answer · 2015-12-17 12:22:21Z

1

JavaScript, 60 Bytes

I know there is already a JS answer here, but wanted to do it without regexes, because regex is really almost a language by itself. I'm sorry if you feel I shouldn't post this, this is my first post.

X is the string to be operated upon.

while((z=x.indexOf('^D'))>0){x=x.slice(0,z-1)+x.slice(z+2);}

Test

Put this into your browser's address bar.

javascript:x=prompt('Enter the sentence to be erased');while((z=x.indexOf('^D'))>0){x=x.slice(0,z-1)+x.slice(z+2);}alert(x);

I love JS because it will let you do things like saying (z=x.indexOf('^D))>0, and it will both assign z.indexOf('^D'); to x and evaluate z.indexOf('^D') in the condition, which saves me precious bytes in this problem. It's not very useful otherwise, but it's fun!

edited Dec 17, 2015 at 12:22

ProgramFOX

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answered Dec 17, 2015 at 11:22

alexcat3

112 bronze badges

3

\$\begingroup\$ No problem posting another answer in a language that was already used. But please note that unless the task specifies otherwise, by default a program or a function is expected. Your is just a snippet. And please post your code in code block markup, so scripts like Code Golf UserScript Enhancement Pack can insert the code size beside the code. \$\endgroup\$
– manatwork
Commented Dec 17, 2015 at 11:31
\$\begingroup\$ Here is the relevant meta consensus regarding snippets as answers. Note that unnamed functions are fine. \$\endgroup\$
– Martin Ender
Commented Dec 17, 2015 at 13:23

Add a comment |

Lord Yuuma · Accepted Answer · 2015-12-27 01:16:16Z

1

Emacs Lisp, 45 73 bytes

(lambda(s)(while(string-match".^H"s)(set's(replace-match"" nil nil s)))s)

Searches for the first occurence of anything else and ^H as long as it exists and replaces it with an empty string.

~~Old, incorrect version~~

(lambda(s)(replace-regexp-in-string".^H"""s))

edited Dec 27, 2015 at 1:16

answered Dec 25, 2015 at 16:46

Lord Yuuma

5972 silver badges2 bronze badges

\$\begingroup\$ Sorry, but I'm afraid this is not enough – you have to do the replacing in multiple steps so “one^Hff^H^H^Huch” gets transformed into “ouch”. \$\endgroup\$
– manatwork
Commented Dec 25, 2015 at 17:03

Add a comment |

manatwork · Accepted Answer · 2016-02-09 14:43:30Z

1

jq 1.5, 41 37 bytes

(34 characters code + 3 characters command line option.)

reduce(./"^H")[]as$t("";.[:-1]+$t)

Sample run:

bash-4.3$ bin/jq -R -r 'reduce(./"^H")[]as$t("";.[:-1]+$t)' <<< "Be nice to this fool^H^H^H^Hgentleman, he's visiting from corporate HQ."
Be nice to this gentleman, he's visiting from corporate HQ.

On-line test (Passing -R through URL is not supported – so input passed as JSON string literal. Passing -r through URL is not supported – check Raw Output yourself.)

edited Feb 9, 2016 at 14:43

answered Jul 14, 2015 at 19:37

manatwork

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Community · Accepted Answer · 2020-06-17 09:04:33Z

Oracle SQL 11.2, 172 bytes

WITH v(s,i)AS(SELECT:1,INSTR(:1,'^')FROM DUAL UNION ALL SELECT LPAD(s,i-2)||SUBSTR(s,i+2),INSTR(s,'^',1,2)-3 FROM v WHERE i>0AND'^'<>s)SELECT s FROM v WHERE INSTR(s,'^')=0;

Un-golfed

WITH v(s,i) AS                        -- Recursive view, s-> string, i->pos of first ^
(
  SELECT :1,INSTR(:1,'^')             -- Initialisation view 
  FROM   DUAL
  UNION ALL
  SELECT LPAD(s,i-2)||SUBSTR(s,i+2),  -- Remove the ^ at pos i and the characters before and after 
         INSTR(s,'^',1,2)-3           -- Compute the pos of the next ^ (the 2nd of s as before the remove just above)
  FROM   v 
  WHERE  i>0                          -- Exit clause : no more ^
    AND  s<>'^'                       -- Needed to circumvent oracle's cycle detection, without it 123^H45^H^H^H78^H will fail
)
SELECT s FROM v WHERE INSTR(s,'^')=0; -- Keep only the row without any ^

coltim · Accepted Answer · 2021-04-10 15:27:51Z

1

K (ngn/k), 23 16 bytes

-7 bytes by rereading question (specifically, "^ will only appear as ^H")

{x_/3#-1+x?"^"}/

Try it online!

Removes one instance of ?^H on each invocation, and is run until convergence (i.e. no more ^'s are present).

{...}/ run function on (implicit) input until it converges
-1+x?"^" get the index of the character immediately prior to the first ^ in x
x_/3# drop the value occurring at that index three times

edited Apr 10, 2021 at 15:27

answered Apr 9, 2021 at 15:55

coltim

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emanresu A · Accepted Answer · 2024-03-04 22:50:15Z

1

Vyxal, 9 bytes

‛^H/ƒλ$Ṫp

Try it Online! Port of caird coinheringaahing's Jelly answer.

   /      # Split on
‛^H       # "^H"
    ƒλ--- # Reduce by
        p # Prepend to the first item
      $Ṫ  # The second with its last item removed

answered Mar 4 at 22:50

emanresu A

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a spaghetto · Accepted Answer · 2015-12-25 15:38:58Z

0

Javascript ES6, 41 39 bytes

f=s=>s==(s=s.replace(/.\^H/,""))?s:f(s)

edited Dec 25, 2015 at 15:38

a spaghetto

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answered Dec 16, 2015 at 22:36

Qwertiy

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Mama Fun Roll · Accepted Answer · 2015-12-30 03:04:27Z

0

𝔼𝕊𝕄𝕚𝕟, 8 chars / 10 bytes (noncompetitive)

ïė/.\^H/

Try it here (Firefox only).

Works like all of the other JSGL's.

edited Dec 30, 2015 at 3:04

answered Dec 29, 2015 at 22:37

Mama Fun Roll

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Erik the Outgolfer · Accepted Answer · 2018-06-03 18:35:57Z

0

APL (Dyalog Unicode), 18 bytes

'.\^H'⎕R''⍠'ML'1⍣≡

Try it online!

answered Jun 3, 2018 at 18:35

Erik the Outgolfer

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macOSisthebestOS · Accepted Answer · 2024-03-05 00:39:13Z

0

Swift, 81 bytes

let f={(s:inout _)in while(s+"").contains("^"){s={s.replacing}()(#/.\^H/#,"",1)}}

Call it like this:

var s = "Horse^H^H^H^H^HCow"
f(&s)
print(s) // "Cow"

answered Mar 5 at 0:39

macOSisthebestOS

1,0091 silver badge12 bronze badges

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Stack Exchange Network

Backhanded^H^H^H^H^H^Hspaces

Leaderboard

49 Answers 49

Jelly, 9 bytes

How it works

Vim, 38 35 bytes

Python 2, 74 + 2 = 76 Bytes

Mumps, 84 Bytes

Java - 123 bytes

Batch - 138 bytes

JavaScript, 60 bytes

bash, 50 bytes

><>, 39 38 36 bytes

JavaScript, 60 Bytes

Test

Emacs Lisp, 45 73 bytes

jq 1.5, 41 37 bytes

Oracle SQL 11.2, 172 bytes

K (ngn/k), 23 16 bytes

Vyxal, 9 bytes

Javascript ES6, 41 39 bytes

𝔼𝕊𝕄𝕚𝕟, 8 chars / 10 bytes (noncompetitive)

APL (Dyalog Unicode), 18 bytes

Swift, 81 bytes

Your Answer

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code-golf
string
or ask your own question.

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Backhanded^H^H^H^H^H^Hspaces

Leaderboard

49 Answers 49

Jelly, 9 bytes

How it works

Vim, 38 35 bytes

Python 2, 74 + 2 = 76 Bytes

Mumps, 84 Bytes

Java - 123 bytes

Batch - 138 bytes

JavaScript, 60 bytes

bash, 50 bytes

><>, 39 38 36 bytes

JavaScript, 60 Bytes

Test

Emacs Lisp, 45 73 bytes

jq 1.5, 41 37 bytes

Oracle SQL 11.2, 172 bytes

K (ngn/k), 23 16 bytes

Vyxal, 9 bytes

Javascript ES6, 41 39 bytes

𝔼𝕊𝕄𝕚𝕟, 8 chars / 10 bytes (noncompetitive)

APL (Dyalog Unicode), 18 bytes

Swift, 81 bytes

Your Answer

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