Reciprocal of a number (1/x)

Question

Challenge

Given a (floating-point/decimal) number, return its reciprocal, i.e. 1 divided by the number. The output must be a floating-point/decimal number, not just an integer.

Detailed specification

• You must receive input in the form of a floating-point/decimal number...
  • ...which has at least 4 significant digits of precision (if needed).
  • More is better, but does not count in the score.
• You must output, with any acceptable output method...
  • ...the reciprocal of the number.
  • This can be defined as 1/x, x⁻¹.
  • You must output with at least 4 significant digits of precision (if needed).

Input will be positive or negative, with absolute value in the range [0.0001, 9999] inclusive. You will never be given more than 4 digits past the decimal point, nor more than 4 starting from the first non-zero digit. Output needs to be accurate up to the 4th digit from the first non-zero one.

(Thanks @MartinEnder)

Here are some sample inputs:

0.5134
0.5
2
2.0
0.2
51.2
113.7
1.337
-2.533
-244.1
-0.1
-5

Note that you will never be given inputs which have above 4 digits of precision.

Here is a sample function in Ruby:

def reciprocal(i)
    return 1.0 / i
end

Rules

• All accepted forms of output are allowed
• Standard loopholes banned
• This is code-golf, shortest answer in bytes wins, but will not be selected.

Clarifications

• You will never receive the input 0.

Bounties

This challenge is obviously trivial in most languages, but it can offer a fun challenge in more esoteric and unusual languages, so some users are willing to award points for doing this in unusually difficult languages.

• @DJMcMayhem will award a +150 points bounty to the shortest brain-flak answer, since brain-flak is notoriously difficult for floating-point numbers

• @L3viathan will award a +150 points bounty to the shortest OIL answer. OIL has no native floating point type, nor does it have division.

• @Riley will award a +100 points bounty to the shortest sed answer.

• @EriktheOutgolfer will award a +100 points bounty to the shortest Sesos answer. Division in brainfuck derivatives such as Sesos is very difficult, let alone floating-point division.

• I (@Mendeleev) will award a bounty of +100 points to the shortest Retina answer.

If there's a language you think would be fun to see an answer in, and you're willing to pay the rep, feel free to add your name into this list (sorted by bounty amount)

Leaderboard

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# Language Name, N bytes

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You can also make the language name a link which will then show up in the leaderboard snippet:

# [><>](http://esolangs.org/wiki/Fish), 121 bytes

var QUESTION_ID=114544,OVERRIDE_USER=62393;function answersUrl(e){return"https://api.stackexchange.com/2.2/questions/"+QUESTION_ID+"/answers?page="+e+"&pagesize=100&order=desc&sort=creation&site=codegolf&filter="+ANSWER_FILTER}function commentUrl(e,s){return"https://api.stackexchange.com/2.2/answers/"+s.join(";")+"/comments?page="+e+"&pagesize=100&order=desc&sort=creation&site=codegolf&filter="+COMMENT_FILTER}function getAnswers(){jQuery.ajax({url:answersUrl(answer_page++),method:"get",dataType:"jsonp",crossDomain:!0,success:function(e){answers.push.apply(answers,e.items),answers_hash=[],answer_ids=[],e.items.forEach(function(e){e.comments=[];var s=+e.share_link.match(/\d+/);answer_ids.push(s),answers_hash[s]=e}),e.has_more||(more_answers=!1),comment_page=1,getComments()}})}function getComments(){jQuery.ajax({url:commentUrl(comment_page++,answer_ids),method:"get",dataType:"jsonp",crossDomain:!0,success:function(e){e.items.forEach(function(e){e.owner.user_id===OVERRIDE_USER&&answers_hash[e.post_id].comments.push(e)}),e.has_more?getComments():more_answers?getAnswers():process()}})}function getAuthorName(e){return e.owner.display_name}function process(){var e=[];answers.forEach(function(s){var r=s.body;s.comments.forEach(function(e){OVERRIDE_REG.test(e.body)&&(r="<h1>"+e.body.replace(OVERRIDE_REG,"")+"</h1>")});var a=r.match(SCORE_REG);a&&e.push({user:getAuthorName(s),size:+a[2],language:a[1],link:s.share_link})}),e.sort(function(e,s){var r=e.size,a=s.size;return r-a});var s={};e.forEach(function(e){var o=e.language;/<a/.test(o)&&(o=jQuery(o).text().toLowerCase()),s[o]=s[o]||{lang:e.language,user:e.user,size:e.size,link:e.link,uniq:o}});var t=[];for(var o in s)s.hasOwnProperty(o)&&t.push(s[o]);t.sort(function(e,s){return e.uniq>s.uniq?1:e.uniq<s.uniq?-1:0});for(var c=0;c<t.length;++c){var i=jQuery("#language-template").html(),o=t[c];i=i.replace("{{LANGUAGE}}",o.lang).replace("{{NAME}}",o.user).replace("{{SIZE}}",o.size).replace("{{LINK}}",o.link),i=jQuery(i),jQuery("#languages").append(i)}}var ANSWER_FILTER="!t)IWYnsLAZle2tQ3KqrVveCRJfxcRLe",COMMENT_FILTER="!)Q2B_A2kjfAiU78X(md6BoYk",answers=[],answers_hash,answer_ids,answer_page=1,more_answers=!0,comment_page;getAnswers();var SCORE_REG=/<h\d>\s*([^\n,]*[^\s,]),.*?(\d+)(?=[^\n\d<>]*(?:<(?:s>[^\n<>]*<\/s>|[^\n<>]+>)[^\n\d<>]*)*<\/h\d>)/,OVERRIDE_REG=/^Override\s*header:\s*/i;

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Answer 1

Elixir, 7 bytes

&(1/&1)

Anonymous function defined using the capture operator.

Full program:

f=
&(1/&1)

IO.inspect(f.(0.5134))  # 1.94779898714453

Try it online!

Answer 2

Emacs Lisp, 11 bytes

(/ 1(read))

Elisp defaults to integer division, so the input will have to be given as floating point, e.g. 1.0 instead of 1. The engine evaluates the (read) statement to get the input and then evaluates the (/ ...) statement, and outputs the answer to stdout.

Answer 3

Bash + bc, 12 bytes

bc -l<<<1/$1

bc defaults to integer division, which would be a problem, but running bc with the -l flag loads a math library that allows for floating point division. The $1 takes the first command line argument passed to the Bash script and the <<< passes the string with the expanded argument to bc.

Answer 4

Pyth, 3 2 bytes

-1 byte thanks to Steven Hewitt

c1

c is float division, with 1 and implicit input.

Answer 5

8087 machine code, 4 bytes

d9 e8   |   fld1
d8 f1   |   fdiv st0, st1

The obvious/trivial solution. Expects input in register st0.

Answer 6

SenseTalk, 16 bytes

params r
put 1/r

Explanation

params r # accept input
put 1/r  # get the reciprocal

Answer 7

Keg, 1 byte

⑱

Try it online!

Keg, 3 bytes(SBCS)

1¿/

TIO Divide 1 by friendly input

Answer 8

W, 3 bytes

You know, we can't beat the built-ins.

1S/

Explanation

a1S  % Stack : 1 a
   / % Divide.(1/a)
     % Output.

Answer 9

NO!, 31 bytes

NO! has 6 valid tokens: NOno!? and commands are made up of NO with the number of O determining the command.

NOOOOO?no!NOOOOOOOOOOO
NOOOOOOOO?no

###More readable

NOOOOO?                 NOOOOO is the divide command and ? starts the arguments
       no!              no is 1 and ! separates the arguments            
          NOOOOOOOOOOO  This takes input from STDIN.

NOOOOOOOO?              This outputs the result of the       line
          no                                           first 

The equivalent pseudocode:

output divide 1, input

Answer 10

HODOR, 100 bytes

Walder
Hodor?!
Hodor, Hodor Hodor Hodor Hodor Hodor Hodor Hodor Hodor Hodor, Hodor,
HODOR!!
HODOR!!!

If you must know how it works, I'll tell you.

Explanation

Walder                                                                       Hodor hodor
Hodor?!                                                                     Hodor hodor hodor HODOR
Hodor, Hodor Hodor Hodor Hodor Hodor Hodor Hodor Hodor Hodor, Hodor,        Hodor hodor hodor hodor hodor hodor
HODOR!!                                                                     Hodor hodor hodor hodor hodor
HODOR!!!                                                                    Hodor hodor (Hodor hodor hodor)

Walder - Start program

Hodor?! - Take input from STDIN

Hodor, Hodor Hodor Hodor Hodor Hodor Hodor Hodor Hodor Hodor, Hodor, - Change accumulator value to it's reciprocal

HODOR!! - Output accumulator value as number

HODOR!!! - Kill Hodor (End the program)

Answer 11

Go, 34 bytes

func(a float64)float64{return 1/a}

Attempt This Online!

Answer 12

Factor, 5 bytes

recip

Try it online!

Answer 13

Pyt, 1 byte

⅟

Try it online!

Just another language with a built-in one-byte reciprocal function

Answer 14

Pascal, 40 bytes

The built-in data type real provides an implementation-defined approximation.

function f(x:real):real;begin f:=1/x end

Answer 15

Jellyfish, 3 bytes

p%i

Try it online!

Unary % computes the reciprocal. i is input, p is output.

Answer 16

Gol><>, 4 bytes

1I,h

Online interpreter link

Answer 17

Dyvil, 5 Bytes

1 / _

Unfortunately we need the extra white space because /_ would be a single operator, and 1/ _ would parse differently

Usage:

let f: double -> double = 1 / _
print(f(2)) // 0.5

Answer 18

Racket 7 bytes

(/ 1 x)

Full function:

(define (f x)
  (/ 1 x))

Testing:

(f 1.56)

Output:

0.641025641025641

Answer 19

REXX, 12 bytes

say 1/arg(1)

Divides 1 by first argument. Precision is decided by NUMERIC DIGITS but defaults to at least 9 decimals.

Answer 20

JavaScript(ES7), 8 bytes

x=>x**-1

f=x=>x**-1;
console.log(f(0.5134));

Answer 21

Python 2.7, 17 25 bytes

Full program:

print'%.4f'%(1.0/input())

Answer 22

CGL (CGL Golfing Language), 6 bytes (non-competing)

This language postdates this challenge.

-÷Ⓧ

Explanation:

- decrements the current stack, so it is now -1, where input is placed

÷ Divides the first element of the stack by the second if it exists, otherwise (this case) it divides 1 by the first (reciprocal)

Ⓧ Output the last stack item (the result of ÷) and exit

Answer 23

Haskell, 4 bytes

(/)1

Currying FTW!

Answer 24

Axiom, 57 bytes

f(x)==(y:=abs(x);y>9999 or y<0.0001=>"ObjFloatErr ";1./x)

test code and results

(21) -> [[i,f(i)] for i in [-2,-1,-0.0001,-0.00001,9999,10000]]
   (21)
   [[- 2.0,- 0.5], [- 1.0,- 1.0], [- 0.0001,- 10000.0],
    [- 0.00001,"ObjError 1/x"], [9999.0,0.0001000100 0100010001],
    [10000.0,"ObjError 1/x"]]

Answer 25

Fourier (Non-Competing), 79 bytes

1~RI~X<0{1}{0-1~R45a}X*R~XL*2+2/2~UX{1}{0~U}10P10/X~DL+U~p10Pp~TD/To*T~A46aD-Ao

Try it online!

This is non-competing for two reasons:

• Firstly, it does not fulfil the spec (it only works for inputs in the range -10 <= x <= 10
• Secondly, it uses the functions L and P which were added after the writing of this challenge

So, this answer poses a challenge: can you complete this challenge in Fourier in the range -9999 <= x <= 9999? There are two bounties up for grabs:

• 100 Rep Bounty for the first solution to complete this task without using the new functions L (log 10) and P (power)
• 50 Rep Bounty for the shortest solution to complete this task using the new functions L (log 10) and P (power)

Note that on the Fourier github repo (https://github.com/beta-decay/Fourier/tree/master/fourIDE/editor) the FourIDE is up to date with L and P.

To-do list

• Add explanation of code

Answer 26

Convex, 1 byte

¹

Try it online!

Answer 27

Jelly , 11 Bytes

²Nṭ1,0ÆrḢ×Ṡ

This works without the built-in inverse function Ị. (Who uses that anyway?).

Try it online!

How it works

²Nṭ1,0ÆrḢ×Ṡ
   1,0      # Look at the list [1,0]
  ṭ         # Append (to the end)
²N          #  the negative of the square of the input
      Ær    # Find the roots to the polynomial with coefficients corresponding to the list as [greater root,lower root] pair
        Ḣ   # Head; get the first element of the roots (always positive)
         ×Ṡ # Multiply by the sign of the input (to accommodate negative input)

Answer 28

Batch, 69 67 + 39 (vbs section) = 106 bytes

a.bat

@for /f "skip=1" %%n in ('cscript //nologo b.vbs 1/%1')do @echo %%n

Explanation:

• call VBScript to calculate 1/argument
• return the result

b.vbs

WScript.Echo Eval(WScript.Arguments(0))

Explanation:(my guess, I'm not good at VBS)

• return the result calculated by Eval

---

Test cases

called from command line:

>a.bat 0.5134
1.94779898714453

>a.bat -0.5
-2

---

Batch can't handle floating point division....

Answer 29

Perl 5, 7 bytes

The obvious subroutine.

{1/pop}

Answer 30

Groovy, 9 bytes

{1.0g/it}

Needs the .0g to denote big decimal notation on the 1, making the it unbox itself as a BigDecimal.

Input of 7.29349129124513204632593467635245678734521456789

Results in 0.13710854789123656486815482305643737234188188122

If you use an input of 214700000000000, however, without the .0g...

You get an error or nothing.