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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Answer 1

GNU sed, 11 bytes

:;s/.^H//;t

Test output:

$ echo "Horse^H^H^H^H^HCow
Be nice to this fool^H^H^H^Hgentleman, he's visiting from corporate HQ.
123^H45^H^H^H78^H
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" | sed ':;s/.^H//;t'
Cow
Be nice to this gentleman, he's visiting from corporate HQ.
17
Digital Trauma
$ 

Answer 2

Pyth, 11 bytes

.U+PbZcz"^H

Demonstration.

.U+PbZcz"^H
               Implicit: z = input()
      cz"^H    z.split("^H")
.U             reduce, with the first element of the list as the initial value.
   Pb          Remove the last character of what we have so far.
  +  Z         And add on the next segment.
               Print implicitly.

Answer 3

Gema, 6 bytes

?#\^H=

Sample run:

bash-4.3$ gema -p '?#\^H=' <<< 'pizza is alright^H^H^H^H^H^Hwesome'
pizza is awesome

CW, because the fool vs. gentleman example takes far too long. (Killed after a day. Maybe a glitch in the interpreter? All other examples here are processed in fractions of seconds.) Gema's recursive pattern not seems to be affected by the recursion level, but the amount of non-matching text increases processing time exponentially.

Answer 4

C, 52 bytes

j;f(char*s){for(j=0;*s=s[j];s[j]==94?s--,j+=3:s++);}

We define a function f that takes a pointer to the string as input. After the function call, that pointer will contain a modified string.

A simple test:

int main(int argc, char** argv) {
    char buf[300] = "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";
    f(buf);
    printf(buf);
    return 0;
}

The above prints:

Digital Trauma

Answer 5

Haskell, 47 bytes

h(a,_:_:b)=f$init a++b;h(x,_)=x
f=h.span(/='^')

Defines a function f :: String -> String. How it works:

    f "ab^Hc^Hd"
=== h ("ab", "^Hc^Hd")   (find ^H)
=== f ("a" ++ "c^Hd")    (backspace)
=== f "ac^Hd"            (join)
=== h ("ac", "^Hd")      (find ^H)
=== f ("a", "d")         (backspace)
=== f "ad"               (join)
=== h ("ad", "")         (find ^H)
=== "ad"                 (no ^H: base case)

Answer 6

CJam, 14 13 bytes

q"^H"/{W\ts}*

How it works

q                   e# Read the entire input
 "^H"/              e# Split it on occurrences of string "^H"
      {    }*       e# Reduce on the split array
       W\t          e# This is the tricky part. We know that if there are two parts that we
                    e# are reducing on, they must be separated by "^H". Which in turn means
                    e# that from the first part, last characters needs to be deleted
                    e# So we simply put the second part in place of the last character of the
                    e# first part.
          s         e# Doing the above makes it a mixed array of character and string.
                    e# So we convert it to a single string, ready to be served as first part
                    e# in next reduce iteration

UPDATE: 1 byte saved thanks to jimmy23013

Try it online here

Answer 7

Retina, 13 bytes

Retina

+`.\^H(.*)
$1

The two lines should go to their own files but you can run the code as one file with the -s flag.

At each step we delete the first match for .\^H in the string. We repeat this (with the + modifier) until no deletion happens.

Answer 8

JavaScript (ES6), 39 bytes

f=s=>(t=s.replace(/.\^H/,''))!=s?f(t):t

// TEST

Out=x=>O.innerHTML+=x+'\n'

Test=_=>(Out(I.value + "\n-> " + f(I.value)),I.value='')

;["Horse^H^H^H^H^HCow"
,"Be nice to this fool^H^H^H^Hgentleman, he's visiting from corporate HQ."
,"123^H45^H^H^H78^H"
,"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"]
.forEach(t => Out(t + "\n-> " + f(t)))

#I { width:400px }

<pre id=O></pre>
<input id=I><button onclick='Test()'>-></button>

Answer 9

Perl, 20 16 15 bytes

(14 characters code + 1 character command line option.)

s/.\^H//&&redo

Sample run:

bash-4.3$ perl -pe 's/.\^H//&&redo' <<< "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.

Answer 10

Julia, 58 42 41 bytes

Saved 16 bytes thanks to manatwork and 1 thanks to Glen O!

f(s)='^'∈s?f(replace(s,r".\^H","",1)):s

This creates a recursive function that accepts a string and returns a string.

This replaces one occurrence of ^H at a time with an empty string while the input contains ^.

Examples:

julia> f("123^H45^H^H^H78^H")
"17"

julia> f("pizza is alright^H^H^H^H^H^Hwesome")
"pizza is awesome"

Answer 11

REGXY, 10 bytes

Uses REGXY, a regex substitution based language. Replaces any character followed by ^H with nothing. The second line then executes which is just a pointer to the previous line, repeating the substitution until it fails to match.

/.\^H//
//

This compiles and executes correctly with the sample interpreter in the link above, but the solution is perhaps a bit cheeky as it relies on an assumption in the vagueness of the language specification. The spec states that the first token on each line (before the /) acts as a label, but the assumption is that a null label-pointer will point back to the first command in the file with a null label (or in other words, that 'null' is a valid label). A less cheeky solution would be:

a/.\^H//
b//a

Which amounts to 13 bytes.

Answer 12

Python 3, 53 bytes

o=""
for x in input().split("^H"):o=o[:-1]+x
print(o)

But personally I like this wordier version better:

H=input().split("^H")
print(eval("("*~-len(H)+")[:-1]+".join(map(repr,H))))

The interesting thing is that

'B''a''c''k''h''a''n''d''e''d'[:-1][:-1][:-1][:-1][:-1][:-1]

actually works and gives 'Back', so I tried to map ^H -> [:-1] and any other char c -> 'c' then eval, but unfortunately you can't have any strings afterwards without a +, so this fails:

'B''a''c''k''h''a''n''d''e''d'[:-1][:-1][:-1][:-1][:-1][:-1]'s''p''a''c''e''s'

Answer 13

Haskell, 52 47 bytes

import Data.Lists
foldl1((++).init).splitOn"^H"

Usage example:

> map (foldl1((++).init).splitOn"^H") ["Horse^H^H^H^H^HCow", "123^H45^H^H^H78^H", "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"]
["Cow","17","Digital Trauma"]

How it works:

                  splitOn"^H"     -- split on substring "^H", e.g "Horse^H^H^H^H^HCow" -> ["Horse","","","","","Cow"]
                 .                -- then
foldl1(         )                 -- fold from left by
            init                  --   first dropping the last char from the left argument
       (++).                      --   second concatenating left and right argument

Answer 14

Ruby, 27 24 20 bytes

(19 characters code + 1 character command line option.)

$_=$`+$'while/.\^H/

Thanks to:

• Ventero for suggesting to use the global variables (-4 characters)

Sample run:

bash-4.3$ ruby -pe '$_=$`+$'"'"'while/.\^H/' <<< "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.

Answer 15

Vim, 12 bytes

qqt^3xh@qq@q

Try it online!

Makes use of the fact that "^ will only appear as ^H".

Explanation

qqt^3xh@qq@q
qq     @qq@q    Define an indefinitely looping recursive macro and immediately call it
  t^            Move to just before the next ^ character in the line
    3x          Delete 3 characters (the one to be deleted, ^, and H)
      h         Move left 1 step (to be in position for the next search)

Answer 16

V (vim), ¹⁶ 14 bytes

qq:s/.^H
@qq@q

Try it online!

similar to sed, but uses Vim's recursion.

Answer 17

Pyth - 19 bytes

Reduce works really, really well with this but it only does one char at a time so I had to spend almost as many chars as the actual algo to do a replace ^H with linebreak. Looking for a better way to do that.

u?+GHnHbPGjbcz"^H"k

Try it online here.

Answer 18

Python 2, 50

It's a bit odd having a second lambda in there, but seems to be the best Python so far.

lambda s:reduce(lambda a,b:a[:-1]+b,s.split('^H'))

Answer 19

Julia, 41 39 bytes

s->foldl((t,v)->chop(t)v,split(s,"^H"))

What it's doing is using ^H as a delimiter, and then removing the last character on each string then concatenating the next string before removing the last character again. Unlike the other Julia answer, this is not a recursive function.

Note: I've removed the function name from the definition. Originally, it said f(s)= rather than s->, and you used it as f("AAA^HB^H^H")... but I'm saving two bytes by letting it be "anonymous", and use itself as its name. You use it like this:

(s->foldl((t,v)->chop(t)v,split(s,"^H")))("AAA^HB^H^H")

(you can also assign a variable to it as f=s->foldl((t,v)->chop(t)v,split(s,"^H")), then f("AAA^HB^H^H") will work)

Answer 20

TeaScript, 7 bytes [Not competing]

Not competing as TeaScript was made after this challenge was posted. This is here as reference.

xW/.\^H

This uses the new TeaScript 3, and recursive replaces to remove the characters

Answer 21

brainfuck, 81 bytes

>,[[>+>+<<-]-[>-<---]>---------[>>+<<[-]]>>-[+<[-]<<<,[-]>>]<[<<+>>-]<,]<[<]>[.>]

Try it online!

Answer 22

Japt, 8 bytes

Ue/.\^H/

Try it online!

How it works

U        // Take the input,
e/.\^H/  // and recursively replace any char followed by "^H" with
         // (nothing, defaults to an empty string).
         // Implicit: output last expression

Answer 23

K5, 64 bytes

K isn't really designed for this kind of work...

{[s]$[2>#s;s;`=t:*&{"^H"~2#x_s}'1+!-2+#s;s;,/2#2!|(0,t,3+t)_s]}/

Answer 24

golflua, 36 bytes

\f(s)@o!=s o=s;s=s:g(".^H","",1)$~s$

Sample run:

Lua 5.2.2  Copyright (C) 1994-2013 Lua.org, PUC-Rio
> \f(s)@o!=s o=s;s=s:g(".^H","",1)$~s$
> w(f("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.

Answer 25

Javascript, 62 bytes

Not the shortest one, but works fine.

t=prompt();while(t.match(R=/.\^H/))t=t.replace(R,'');alert(t);

This probably can be shortened a lot!

Answer 26

R, 54 52 bytes

f=function(s)ifelse(s==(r=sub(".\\^H","",s)),r,f(r))

Same basic idea as my Julia answer. This creates a recursive function that accepts a string and returns a string. If the input is equal to itself with a single occurrence of ^H removed, return it, otherwise call the function again.

You can try it online!

Answer 27

ECMAScript 6, 57 bytes

s=>{while(~s.indexOf`^H`)s=s.replace(/.\^H/,'');return s}

This is probably golfable, just gotta think of a way probably not

Answer 28

Java, 78 77 bytes

String f(String a){while(!a.equals(a=a.replaceFirst(".\\^H","")));return a;}

Answer 29

(Visual)FoxPro any version 80 bytes

PARA t
DO WHILE AT('^H',t)>0
t = STRT(t,SUBS(t,AT('^H',t)-1,3))
ENDDO
RETU t

Repeating string translation to empty by finding ^H and backing up one character.

Answer 30

rs, 8 bytes

Technically, this doesn't count, as it depends on a feature I added after this question was posted. However, I think it's pretty neat.

+?1.\^H/

Live demo and test cases.