How long is this string, really?

Question

In most programming languages, the string Hello, World! can be represented as "Hello, World!". But if you want to represent "Hello, World!" you need to escape the double quotes with backslashes for "\"Hello, World!\"", and to represent that you also need to escape the backslashes resulting in "\"\\\"Hello, World!\\\"\"".

Your challenge is to, given a printable ASCII string that's been escaped multiple times (such as "\"\\\"Hello, World!\\\"\"", find how many characters it is when fully unescaped. Specifically, you should remove a single pair of enclosing " and replace \\ with \ and \" with ", until there are no more enclosing " left.

You can assume that the string will be syntactically valid - At all stages, as long as the string starts and ends with ", all other backslashes and double quotes will be properly escaped, and only " and \ will be escaped. The input string will not be " at any level of escaping. If the string starts and ends with ", the last " cannot be escaped, so e.g. "abc\" won't occur.

This is code-golf, shortest wins!

Testcases

e -> 1
"hello" -> 5
"\"\\" -> 2
a""b"c -> 6
"c\d+e -> 6
"\"\\\"Hello, World!\\\"\"" -> 13
"c\\\"d\"" -> 5
"\"\"" -> 0
"r\"\"" -> 3
"\"hello\"+" -> 8
"\"\\\"\\\\\\\"\\\\\\\\\\\\\\\"Hello\\\\\\\\\\\\\\\"\\\\\\\"\\\"\"" -> 5
"\\\\\"" -> 3
[""] -> 4

• l4m2: Is it required to handle [""] or other valid JSON corrently?
• caird coinheringaahing: Effectively the opposite task
• emanresu A: @l4m2 Yes, I'll add that as a testcase
• emanresu A: @Jakav I'm going to only allow using ", because allowing ' opens the door to backticks and various other types of quotes that deviate a bit from the intent of the challenge.
• emanresu A: @NickKennedy Backslashes will only escape double quotes and other backslashes, so "\n" won't occur. Since it's a weird edgecase I'll say " won't occur

Answer 1

JavaScript (Node.js), 41 bytes

f=x=>/^".*"$/.test(x)?f(eval(x)):x.length

Try it online!

Trivial

Answer 2

Jelly, 11 bytes

ŒV.ị=""ȦƲ¿L

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-2 bytes thanks to Jonathan Allan

Explanation

ŒV.ị=""ȦƲ¿L Main Link
 ------Ʋ Link Grouping (see below)
 ¿ While
 .ị the first and last (index at 0.5)
 Ȧ are all
 ="" equal to "
ŒV Evaluate (Python)
 L Length

The footer runs all tests and prints 1 for any correct answers. Ỵœṣ" -> "$€Ç=V}ɗ/€ means "split on newlines, split each string on substrings equal to " -> ", then for each pair, check that the result of the main link on the left side equals the right side evaluated (to convert to a number)".

For the link grouping, Ʋ combines four links into a monad, so you'd think we'd need to use $ to capture the fifth, but since ""Ȧ would be an LCC (a chain that begins with a nilad and only has monads and dyad-nilad/nilad-dyad pairs after it, so a chain with a constant result), it doesn't count that as a link and therefore keeps going one extra time. This is an important tip when understanding the link combining quicks as all of them do this and it is easy to miscount or misunderstand the grouping because it may be taking more links than you expect.

ŒV.ị=)""Ʋ¿L would also work where instead of =""Ȧ to check that all are equal to ", we just check that it's equal to ['"', '"']. This also makes the grouping a bit simpler because we don't have any potential LCCs so it just takes four links.

• Nick Kennedy: I’m clarifying, but I think this fails for the following input: ". It crashes rather than returning 1.
• Nick Kennedy: The OP has clarified that " won’t occur so you’re all good!
• Kirill V. Lyadvinsky: The code has 11 characters, but it is 19 bytes actually.
• hyperneutrino: @KirillV.Lyadvinsky Jelly uses its own encoding so all 256 of the characters it uses occupy 1 byte each.

Answer 3

Retina 0.8.2, 47 bytes

+`(?=.*"$)(^"(?!$)|\\(.)|(?!^)"$)(?<=^".*)
2ドル
.

Try it online! Link includes test cases. Explanation:

(?=.*"$)

Ensure the string ends with a " before making any replacements.

(^"(?!$)|\\(.)|(?!^)"$)

Replace a leading ", an escaped character or a trailing ", but not a lone ".

(?<=^".*)

Ensure that the string starts with a " before making any replacements.

2ドル

Unescape the character.

+`

Repeat until the string can't be unquoted further.

.

Get the length of the final string.

If " is excluded as being an unsupported input, then ten bytes can be saved by removing (?!$) and (?!^).

Answer 4

Excel ms365, 138 bytes

Assuming input in A1:

=LET(x,LAMBDA(f,s,IF(s<"",s,f(f,IFNA(SUBSTITUTE(SUBSTITUTE(MID(s,XMATCH("""*""",s,2)+1,LEN(s)-2),"\\","\"),"\""",""""),LEN(s))))),x(x,A1))

It's a recursive LAMBDA that will keep calling itself untill no more starting+leading double quotes.

---

Google Spreadsheets, 107 bytes

Again, assuming input in A1, applying the same recursive logic with a few slight changes making use of the regex-functions:

=LET(x,LAMBDA(f,s,IF(REGEXMATCH(s,""".*"""),f(f,REGEXREPLACE(s,"^""|""$|\\(\\|"")","1ドル")),LEN(s))),x(x,A1))

• doubleunary: Use regexmatch(s,"^"".*""$") to cover all test cases?

Answer 5

Perl 5 -pl, 45 bytes

s/\\(\\|")/1ドル/g while s/^"(.*)"$/1ドル/;$_=y///c

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Perl 5 -pl, 54 bytes

Handles the "\"foo\\\"" testcase I proposed in the comments. If that's not a valid test case, then the shorter version above will suffice.

s/\\(\\|")/1ドル/g while s/^"(.*[^\\])"$/1ドル/;say;$_=y///c

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• Nahuel Fouilleul: just 1 byte less Try it online!
• Neil: Your second version fails on "\"foo\\\\\"", which is a legal input for the first version. (Also it has a spare say; which you don't need.)
• Neil: Oh, and is there any reason not to use s/\\(.)/1ドル/g?

Answer 6

Python, (削除) 51 (削除ここまで) 52 bytes

f=lambda s:f(eval(s))if'"'==s[-1:]==s[:1]else len(s)

Not complicated, but it works well.

Explanation:

Define a function f that takes an argument s:

f=lambda s:

If the string begins and ends with ", return the value of the function with backslashes evaluated:

f(eval(s))if'"'==s[-1:]==s[:1]

Otherwise, output the length of the string:

len(s)

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• Neil: Reversing your condition order if'"'==s[0]==s[-1] saves a byte.
• l4m2: Crash when result is 0
• Nick Kennedy: I’m clarifying, but I think this fails for the following input: ". It crashes rather than returning 1.
• l4m2: @NickKennedy I'd say " is invalid input but "" is
• Nick Kennedy: The OP has clarified that " won’t occur so you’re all good!

Answer 7

Charcoal, (削除) 34 (削除ここまで) 33 bytes

W¬∨⌕θ"⌕⮌Φθλ"≔⪫−⪪✂θ1±1¦1\\¦\¦\θILθ

Try it online! Link is to verbose version of code. Explanation:

W¬∨⌕θ"⌕⮌Φθλ"

Repeat while the string starts with " and ends with a different "...

≔⪫−⪪✂θ1±1¦1\\¦\¦\θ

... remove those "s, split the string on \\, remove any remaining \s, then join the string on \, thus unquoting the string.

ILθ

Output the length of the final string.

(Yes I could use eval to save 14 bytes but that's boring.)

If " is excluded as being an unsupported input, then two bytes can be saved by replacing Φθλ with θ.

Answer 8

Python 3, (削除) 91 (削除ここまで)90 bytes

f=lambda s:f(s[1:-1].replace('\\"','"').replace(r'\\','\\'))if'"'==s[-1:]==s[0]else len(s)

because eval is evil :P, with inspiration from Jakav

Try it online!

• noodle person: Welcome to Code Golf SE, nice first answer! I think .replace('\\"','"').replace(r'\\','\\') can be shortened to just .replace('\\','') maybe? Not sure though.
• David_h: @noodleman that was what I was initially thinking, but unfortunately it breaks with something like "\\\\\""
• noodle person: Ah, right, that makes sense
• l4m2: if'"'==s[-1:]==s[0]

Answer 9

QBASIC, 302 bytes

Q$ = CHR$(34): LINE INPUT T$: DO WHILE LEFT$(T,ドル 1) + RIGHT$(T,ドル 1) = Q$ + Q$: U$ = MID$(T,ドル 2, LEN(T$) - 2): T$ = "": C$ = "": FOR J = 1 TO LEN(U$): C$ = C$ + MID$(U,ドル J, 1): B = -(C$ <> "\"): T$ = T$ + RIGHT$(C,ドル B * ((INSTR("\\" + Q,ドル C$) > 0) + 2)): C$ = LEFT$(C,ドル 1 - B): NEXT: LOOP: PRINT LEN(T$)

A bit of nostalgia...

Explanation:

'Set quote mark because QBASIC doesn't have string escaping 
'then get string
Q$ = CHR$(34)
LINE INPUT T$
'Process the string while it starts and ends with quotes
DO WHILE LEFT$(T,ドル 1) + RIGHT$(T,ドル 1) = Q$ + Q$
 'Strip enclosing quotes, assign to a temporary variable,
 'prepare to rebuild the original string,
 'and prepare to track current character(s)
 U$ = MID$(T,ドル 2, LEN(T$) - 2)
 T$ = ""
 C$ = ""
 'Process string character by character.
 FOR J = 1 TO LEN(U$)
 'Add current character to current status
 C$ = C$ + MID$(U,ドル J, 1)
 'QBASIC boolean ops return -1 for true, 0 for false,
 'so set B to 0 if current character is an escape char, to 1 otherwise.
 B = -(C$ <> "\")
 'Add current character to string if not an escape char,
 'de-escaping if appropriate
 T$ = T$ + RIGHT$(C,ドル B * ((INSTR("\\" + Q,ドル C$) > 0) + 2))
 'Clear current character unless it's an escape char
 C$ = LEFT$(C,ドル 1 - B)
 NEXT
LOOP
PRINT LEN(T$)

Answer 10

05AB1E, 10 bytes

Δ¬'"Qi.E]g

Try it online or verify all test cases. (Note: in the single TIO, the input is wrapped within """-quotes to always have a string input.)

Explanation:

Δ # Loop until the result no longer changes:
 ¬ # Push its first character (without popping the string)
 '"Qi '# If it's a double quote:
 .E # Evaluate the string as Elixir code
] # Close both the if-statement and changes-loop
 g # Pop and push the length of the reduced string
 # (which is output implicitly as result)

Answer 11

Pyth, 20 bytes

L?&b&qhbNqebNyvblbyw

Try it online!

Same approach as Jakav's Python solution.

Answer 12

Vyxal l, 70 bits^v2 , 8.75 bytes

Sλh\"=ßE;Ẋ

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Bitstring:

0110001110110011010000001101101101100000011010011000101001000111010000

Port of 05ab1e except i had to add a "stringify" at the start for the final case