Build an octal calculator that can do the following operations:

  • Add (+)
  • Subtract (-)
  • Multiply (*)
  • Divide (/)
  • Check is prime

Counting in octal is like this with decimal

(Octal)  (Decimal)
0        0
1        1
2        2
3        3
4        4
5        5
6        6 
7        7
10       8
11       9

and so on...

So given input a b c

  • a being a number in octal
  • b being an operator (+, -, *, /) not is prime
  • c being a number in octal

Output the expression evaluated as abc = Output (Is prime)

Test cases:

a=3, b='+', c=3 -> 6 (false)

a=5, b='+', c=5 -> 12 (false)

a=1, b='*', c=5 -> 5 (true)

a=7, b='+', c=6 -> 15 (true)

a=31, b='-', c=11 -> 20 (false)

a=25, b='/', c=3 -> 7 (true)


  • The output just needs to contain the answer and a truthy/falsey value of whether it is prime so [4,0] is fine.
  • The inputs will always be a case that outputs an integer (integer division)
  • This is code golf so shortest answer wins

When is an octal number a prime


closed as unclear what you're asking by programmer5000, Cody Gray, TheLethalCoder, Titus, Toto Jul 25 '17 at 9:07

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  • \$\begingroup\$ Can we do something like [12, 0] or [4, 1] instead of 12 (false) and 4 (true)? \$\endgroup\$ – Stephen Jul 19 '17 at 13:10
  • \$\begingroup\$ Yes, will ammend. \$\endgroup\$ – LiefdeWen Jul 19 '17 at 13:11
  • 7
    \$\begingroup\$ ...as if being octal is a property of numbers... \$\endgroup\$ – Leaky Nun Jul 19 '17 at 13:12
  • 1
    \$\begingroup\$ Also, does division refer to integer division? \$\endgroup\$ – Erik the Outgolfer Jul 19 '17 at 13:14
  • 1
    \$\begingroup\$ @totallyhuman, you have to take 3 seperate strings though. \$\endgroup\$ – LiefdeWen Jul 19 '17 at 14:07

Mathematica, 38 bytes


Anonymous function. Takes input in the form ... &[Plus, {"7", "12"}] (with both numbers as octal strings and the operator being Plus, Subtract, Times, or Divide) and returns output in the form {17, True} (with the number in decimal.) Did this based on my own, possibly incorrect, interpretation of the rules; please comment if I did something wrong.


05AB1E, 13 bytes


Try it online!

Input format:


Output format:

[Is prime, 'Output']

Note that strings and numbers are equivalent datatypes in 05AB1E.

  • \$\begingroup\$ Hmm...not sure if valid. \$\endgroup\$ – Erik the Outgolfer Jul 19 '17 at 13:25
  • \$\begingroup\$ @MagicOctopusUrn I don't think it'd behave correctly (also there's ð for ' ), since the operator is designed to work on base-10 ints, while it would have incorrect results with base-8 ints. Also you aren't supposed to check if the base-8 version is prime, but the integer itself before converting to base-8 with 8B. \$\endgroup\$ – Erik the Outgolfer Jul 19 '17 at 14:21
  • \$\begingroup\$ No it still makes the operator work on the base-8 versions of the integers (something it's not supposed to do). Basically it would treat them as base-10 integers. \$\endgroup\$ – Erik the Outgolfer Jul 19 '17 at 14:23
  • \$\begingroup\$ Back to disliking the challenge, get it now though. \$\endgroup\$ – Magic Octopus Urn Jul 19 '17 at 14:25

JavaScript, 82 bytes



Input is in octal base, output is also in octal base.


Jelly, 12 bytes


Try it online!

Uses × for * and ÷ or : for / (approved by OP in chat).

Argument 1:

[a, c] 

Argument 2:



[Output, Is prime]

Python 2, 89 67 bytes

A whopping -22 bytes thanks to suggestions by Rod.

print[oct(n),all(n%i for i in range(2,n))]

Try it online!

Takes input as:

['01', '*', '05']

Prints a list like:

['05', True]
  • 1
    \$\begingroup\$ You can drop both lambdas switching to input()/print to save 2 bytes, also since you are using eval, you don't need to convert to int(,8), you can use octa literals in the string to save 10+ \$\endgroup\$ – Rod Jul 19 '17 at 13:53
  • \$\begingroup\$ 1 is shown prime you need to add x>1and I guess. \$\endgroup\$ – officialaimm Jul 19 '17 at 14:21

PHP, 104 bytes


Run with -nr or try it online.

Output format: Result_1 for primes; Result_ for non-primes.

Output for negative results is faulty; replace the echo part with echo$n<0?-decoct(-$n):decoct($n),_,$i==1; (+17 bytes) to fix.


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