# Invert a boolean array

A nice simple one

# Input

Given a boolean array (Or an acceptable alternative), you can assume the array will never be more than 32 elements long.

[false, false, true, false, false]


# Output

Invert every element of the array and output it.

[true, true, false, true, true]


# Rules

• You can write a full program or just a function
• Standard loopholes apply
• Shortest code in bytes, per language, wins!

# Test cases

Input:
[true, false]
Output:
[false, true]

Input: //Example of acceptable alternative
[0,1,1]
Output:
[1,0,0]

• How about arrays of 0 (false, all 0 bits) and -1 (true, all 1 bits)?
– lynn
Commented Sep 15, 2016 at 11:52
• @Lynn While it's the OPs decision, I'd say it should be up to whether your language considers though truthy/falsy. Commented Sep 15, 2016 at 11:53
• Related. (Given the simplicity of the core task, I'd say the differences in format are significant enough that these aren't duplicates.) Commented Sep 15, 2016 at 12:28
• More than code golf this looks to me like: what is the not operator in your favourite language? Additional points if it works on lists. Commented Sep 15, 2016 at 23:32

# Arturo, 15 bytes

$=>[map&=>not?]  Try it # Thunno 2, 1 byte ~  Attempt This Online! Built-in for vectorised logical NOT. # Japt-m, 2 bytes ^1  Try it here ## C, 37 bytes f(a,l)int *a;{for(;l--;*a++=*a?0:1);}  a being the array (pointer) and l being the length of the array. Readable version f(t,i)int *t;{ // K&R to save bytes for(;i--; // Run i times *t++=*t?0:1); // Flip the value of array element and increment }  # Java, 51 bytes l.stream().map(b->!b).collect(Collectors.toList());  l = a Collection of Booleans I feel like this could be shorter, then again golfing in java ^^ • Unless the challenge says otherwise, all submissions need to be full programs or callable functions, as opposed to snippets which expect the input to be stored in a hardcoded variable. The shortest fix would probably be to wrap what you've got in a simple function body (or lambda, depending on Java version). Commented Sep 15, 2016 at 12:48 • As alternative, you can use streams directly: s->s.map(b->!b). I'm currently asking on meta if this is acceptable or not. Commented Sep 15, 2016 at 13:58 • Hmmm... Also, you don't reference the packages, either in import or full text. Commented Sep 15, 2016 at 14:29 • If s->s.map(b->!b) that @OlivierGrégoire already posted wasn't allowed, you could still golf it by returning an Object-array l->l.stream().map(b->!b).toArray() instead (also, as stated by others, your current solution isn't valid. It should have a leading l->; Collectors should be java.util.stream.Collectors; and you can drop the trailing ;). Commented Jan 24, 2018 at 15:24 # PHP , 45 Bytes <?foreach($_GET[a]as$v)$a[]=1-$v;print_r($a);

• As the question states 'Invert every element of the array and output it.' and people aren't usually too picky on output format, save 6 bytes by doing print_r($a); at the end Commented Sep 15, 2016 at 16:13 • Okay I'll try it Commented Sep 15, 2016 at 16:22 • You don't need the spaces there. Your whole code can be written as <?foreach($_GET[a]as$v)$a[]=1-$v;print_r($a);. This saves 2 bytes and works. Commented Sep 15, 2016 at 20:43

## Common Lisp, 7

bit-not


Negate bits on a bit array.

## Example

(bit-not #*00101010010100101001010010101)
=> #*11010101101011010110101101010


# Swift(2.2) 44 bytes

I am using x as the input variable here. For example,

let x = [true,false]


¯\_(ツ)_/¯

### Golfed

let y = {let b = $0.map({!$0});print(b);}(x)


### unGolfed

let y = {
let b = $0.map({!$0})
print(b);
}(x)


# PHP (231 Bytes)

function flip_bool_array($array) {$newarray = array();
foreach ($array as$bool) {

if ($bool === true) {$bool = false;
} else {
$bool = true; }$newarray[] = $bool; } return$newarray;

}


## Explanation

The function accepts an array and loops over it testing each value for a true value and setting it to false, if the value is not true then it is set to true. Each boolean is added to a new array and returned.

• Welcome to the site! You could take a ton of bytes off if you remove the extra whitespace, and shorten your variable names down to one letter each. Since the goal is just short code, readability is not important. Also, there's a great thread here for tips on golfing PHP code down further. Commented Sep 16, 2016 at 21:28

# Ruby, 30 bytes

gets.split(?,).map{|e|!eval e}


"true,false" outputs false,true.

• @EasterlyIrk Sorry didn't know about that. Newbie here Commented Sep 16, 2016 at 15:53

# dc, 44 bytes

Append this to a line of space-delimited input and echo it into dc. Output is delimited with newlines and punctuated with error messages (due to the blatant abuse of k). If you quote the stuff, it'll give you even more errors. (When we re-vamp dc in the next version, we should probably do something about that.) I suggest pairing with a 2>nul or other system-specific hack for suppressing whiny programs.

0sz[1r-SAlz1+szz0<a]dsax[lzd1-szLApk0<a]dsax


Explained:

              # "ToS" := "top of stack"
0sz           # Initialise register z' with 0: this will hold the length of our input
[             # Open macro definition
1r-          #  Replace ToS with !(ToS): 1-1==0, 1-0==1
SA           #  Store this result on the top of stack A'
lz1+sz       #  Increment z, our length counter
z0<a         #  If the stack depth is positive, repeat (we still have input to negate)
]dsax         # Store a copy of macro in register a' and execute it
# At this point, our input has been negated and stored in A,
#  first-in-first-out orientation
[             # Open macro definition
lzd1-sz      #  Decrement z and keep a copy of it for later
LA           #  Push ToS(A) onto stack; pop from A
p            #  Peek at ToS
k            #  k' is for KILL THE TOP OF STACK BWAHAHAHA
0<a          #  The value from register z' is now on top: if positive, we still have
#   values to print, so repeat macro
]dsax         # I'm in a chaotic mood, so let's just re-use a'

• If you prefer space-delimited output: s/pk/n32P/
– juh
Commented Sep 17, 2016 at 8:26

# Emacs Lisp, 25 bytes

(lambda(x)(mapcar'not x))


Not very creative.

## Racket 11 bytes

(map not l)


Testing:

(define l '(#t #f #t)) ; define a list of booleans

(map not l)


Output:

'(#f #t #f)


# ><> Fish - 9 (16?) Bytes

My second golf and my first in ><> Fish!

l?!;r0=nr


I'm not sure how to count bytes when flags are considered, but this solution works when running the python interpreter with the -v flag and then space-separated 1's and 0's. If this doesn't match spec, I can remove the answer.

## Example

Input/Run:

python fish.py --code "l?!;r0=nr" -v 0 1 0 1 1


Output:

10100


If I'm not allowed to use flags, and instead need to take the input from the input stack (such as on https://fishlanguage.com/playground), the code becomes longer as I must read from the input stack (either 1 or 0 without any separation) until there are no more values, and then convert the char value of the input (1 becomes 49 and 0 becomes 48) to their decimal values before my comparison. I'm not sure how to count bytes for ><> but I believe this would be 16 bytes.

i:1+?!;f3*3+-0=n


## dc, 47 bytes

?zsN0sI[z:az0<A]dsAx[lI1+ddsI;a1r-n32PlN>R]dsRx


The actual code to invert a boolean (0 or 1) is 1r-. The rest is for reading the list and printing it in the same order, which is quite hard because of the (LIFO) stack that dc uses to store the input.

Explanation:

?zsN0sI         # read input, LIFO, initialize N = nr_elements and I = 0 (iterator)
[z:az0<A]dsAx   # loop A: move the stack content into array 'a' (I add a[n] first,
#then a[n-1], ..., then a[1] and a[0] is not used)
[lI1+ddsI;a     # loop R: increment iterator and push a[I] to stack (input order)
1r-n32P         #invert value and print it with a space separator
lN>R]dsRx       #repeat (R)


Run:

dc -f invert_boolean.dc <<< "1 0 1 1"


Output: there is a trailing separator (space) at the end, but I hope that's ok

0 1 0 0


Note: my answer is similar in concept to that of @Joe's, but there are differences in terms of I/O handling, stack manipulation (I use arrays) and lack of warnings. Do check his answer as well.

# dimwit 8 bytes (non-competing)

R1,0}0,1


Replaces all 0's with 1's, and vice versa.

Takes input through a string of 0's and 1's, and outputs similarly. Hopefully that's acceptable ;)

### Try it here!

• Yes, it is :) ...# Commented Sep 23, 2016 at 18:56

# SmileBASIC, 25 bytes

DEF l l
ARYOP 1,l,1,l
END


### Explanation:

DEF 'create a function
l 'named "L"
l 'with 0 outputs and 1 input named "L"
ARYOP 'array operation
1 'mode 1 (subtract)
,l 'set each element in L to...
,1 '1 minus...
,l 'the corresponding element in L
END 'end function definition


[49^$0>][-.]#  Input is a list of 0 and 1 characters. # Tcl, 31 bytes proc N L {lmap b$L {expr !$b}}  Try it online! # Zsh, 14 bytes Assumes input is given as arguments. Try it Online! for z;<<<$[!z]


Or without bending the rules so much, this uses array I/0 (26B):

for z ($A)B+=($[!z])
<<<$B  # MMIX, 24 bytes (6 instrs) 00000000: 25010101 82ff0001 73ffff01 a2ff0001 %¢¢¢²”¡¢s””¢ɱ”¡¢ 00000010: 5901fffc f8000000 Y¢”‘ẏ¡¡¡  Requires at least one element. Pass array as first argument, length as second. invarr SUB$1,$1,1 // loop: i-- LDBU$255,$0,$1
ZSZ  $255,$255,1
STBU $255,$0,$1 // a[i] = !a[i] PBNN$1,invarr      // if(i >= 0) goto loop
POP  0,0


# Erlang, 43 38 bytes

n(Z)->lists:map(fun(X)->not X end,Z).

Many thanks to @Redwolf Programs for saving 5 bytes.

• I don't know Erlang, but can any of that whitespace be removed? Commented May 14, 2021 at 21:46