What do you get when you multiply 6 by 9? (42)

Question

I love math. But I can't find a single calculator that can multiply correctly. They seem to get everything right except 6*9 (It's the question to life, the universe, and everything! How could they get that wrong?!). So I want you all to write a function for me that can multiply 2 numbers correctly (and 6*9 equals 42 instead of 54. 9*6 equals 54 still).

Oh, and I'm going to have to build the source in Minecraft so... fewest bytes win!

Recap

• Take 2 numbers as input (type doesn't matter, but only 2 items will be passed, and order must be consistent. So streams, and arrays are ok as long as they preserve the order they where passed in. I.e., a map won't work because it doesn't preserve the order)
• Output multiple of both numbers except if they are 6 and 9, then output 42 (order matters!)
  • PS. I never was really good with counting, so I think only integers from 0 to 99 are real numbers (type used doesn't matter)
• Fewest bytes per language wins!

Leaderboard:

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Answer 1

Mathematica, 15 bytes

Byte count assumes Windows ANSI encoding (CP-1252).

6±9=42
±n__:=1n

Defines a binary operator ± which solves the problem. We simply define 6±9=42 as a special case which takes precedence and then add a fallback definition which makes ± equal to multiplication. The latter uses a fairly interesting golfing trick. The reason this works is actually quite elaborate and we need to look into sequences. A sequence is similar to what's known as a splat in other languages. It's basically a "list" without any wrapper around it. E.g. f[1, Sequence[2, 3, 4], 5] is really just f[1, 2, 3, 4, 5]. The other important concept is that all operators are just syntactic sugar. In particular, ± can be used as a unary or binary operator and represents the head PlusMinus. So ±x is PlusMinus[x] and a±b is PlusMinus[a,b].

Now we have the definition ±n__. This is shorthand for defining PlusMinus[n__]. But n__ represents an arbitrary sequence of arguments. So this actually adds a definition for binary (and n-ary) usagess of PlusMinus as well. The value of this definition is 1n. How does this multiply the arguments? Well, 1n uses Mathematica's implicit multiplication by juxtaposition so it's equivalent to 1*n. But * is also just shorthand for Times[1,n]. Now, n is sequence of arguments. So if we invoke a±b then this will actually become Times[1,a,b]. And that's just a*b.

I think it's quite neat how this syntax abuse lets us define a binary operator using unary syntax. We could now even do PlusMinus[2,3,4] to compute 24 (which can also be written as ±##&[2,3,4] or 2±Sequence[3,4] but it's just getting crazy at that point).

Answer 2

Haskell, 14 bytes

6&9=42
a&b=a*b

Try it online!

Answer 3

C, 32 31 29 28 bytes

^{-2 thanks to Digital Trauma
-1 thanks to musicman523}

#define f(a,b)a^6|b^9?a*b:42

Pretty simple. Declares a macro function f that takes two arguments, a and b.
If a is 6 and b is 9, return 42. Otherwise return a x b.

Try it online!

Answer 4

JavaScript (ES6), 20 bytes

x=>y=>x-6|y-9?x*y:42

Explanation:

Iff x==6 and y==9, x-6|y-9 will be 0 (falsy), and 42 will be the result.

Snippet:

f=

x=>y=>x-6|y-9?x*y:42

console.log(f(6)(9));
console.log(f(9)(6));

Answer 5

Python 2, 30 29 bytes

Thanks to Jonathan Allan for saving a byte!

lambda x,y:x*[y,7][6==x==y-3]

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Answer 6

05AB1E, 15 11 9 bytes

-4 bytes thanks to @Emigna

-2 bytes thanks to @Adnan

P¹69SQi42

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How it works

P          # multiply input
 ¹         # push first number
  69       # the number 69
    S      # split per character
     Q     # equality for both inputs
       i42 # if so, print 42
           # otherwise print product

Answer 7

Java (OpenJDK 8), 24 22 bytes

-2 bytes thanks to @OlivierGrégoire

a->b->a==6&b==9?42:a*b

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Answer 8

Ruby, 24 bytes

->a,b{a==6&&b==9?42:a*b}

Answer 9

Brain-Flak, 158 154 148 140 138 126 bytes

(({}<>)(((([()()()]<>)){})<({}{}({}))>{(()()()){}(<{}>)}{}))([()]{()(<{}>)}{})(({<{}>{}((<>))}{}){}<{}>{<({}[()])><>({})<>}{})

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Explanation

This code is pretty simple. We make copies of the top two items on the stack, we subtract 6 from one and 9 from the other. We then take the not of the two values. We and those values, multiply the result by 12. Multiply the inputs and subtract the two results.

Answer 10

Factorio, 661 bytes, 6 combinators with 9 connections

There is one constant combinator set to output A and B. Change these to set the input.

Blueprint string (0.15.18):

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

The output is signal Z and is to be taken from the top and bottom deciders.

Answer 11

Jelly, 8 7 bytes

Vf96SạP

Input is as an array of two integers: first the right operand, then the left one.

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How it works

Vf96SạP  Main link. Argument: [b, a]

V        Cast [b, a] to string, then eval the resulting string.
         For [b, a] = [9, 6], this yields 96.
 f96     Filter with 96, yielding [96] if V returned 96, [] otherwise.
    S    Take the sum, yielding either 96 or 0.
      P  Compute the product of [b, a], yielding ba = ab.
     ạ   Compute the absolute difference of the results to both sides.
         When the sum is 0, this simply yields the product.
         However, when [b, a] = [9, 6], this yields 96 - 54 = 42.

Answer 12

Factorio, 581 bytes, 3 combinators with 4 connections

Blueprint string (0.16.36):

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

The bottom left constant combinator should be set to output A and B as input. The output is signal Z from the bottom right arithmetic combinator.

Top left: 2147483640 A, 2147483637 B
Top right: If everything = 2147483646 output B, input count
Bottom left: (input) A, (input) B
Bottom right: A * B -> Z

Answer 13

MATL, 11 bytes

[BE]=?42}Gp

Input is an array with the two numbers.

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Explanation

[BE]    % Push array [6, 9]
=       % Implicit input: array of two numbers. Compare with [6, 9] element-wise
?       % If the two entries are true
  42    %   Push 42
}       % Else
  G     %   Push input
  p     %   Product of array
        % Implicit end. Implicit display

Answer 14

R, 33 bytes

function(a,b)`if`(a-6|b-9,a*b,42)

Returns a function.

Try it online!

Answer 15

GW-BASIC, 55 bytes

1INPUT A:INPUT B
2IF A=6THEN IF B=9THEN ?"42":END
3?A*B

Output:

The first machine at pcjs has IBM BASIC, which is practically the same thing. To test this, head over there, hit Run on the machine, Press Enter-Enter and type BASICA to get into BASIC mode. Then enter the source code (it will automatically prettyprint for you), type RUN, input two integers, and done!

Answer 16

JavaScript (ES6), 25 bytes

x=>y=>[x*y,42][x==6&y==9]

Answer 17

Check, 34 33 bytes

.:+&>#v
#>42#v#9-!\>6-!*?
 d* ##p

Check is my new esolang. It uses a combination of 2D and 1D semantics.

Input is two numbers passed through command line arguments.

Explanation

The stack starts with the command line arguments on it. Let's call the arguments a and b.

The first part, .:+&, essentially duplicates the stack, leaving it as a, b, a, b. > pushes 0 to the stack (it is part of a numeric literal completed by 9).

# switches to 2D semantics, and v redirects the IP downwards. The IP immediately runs into a #, which switches back to 1D semantics again.

9-! checks whether b is equal to 9 (by subtracting 9 and taking the logical NOT). \>6-! then checks whether a is equal to 6. The stack now contains a, b, 1, 1 if and only if b==9 and a==6. Multiplying with * takes the logical AND of these two values, giving a, b, 1 if the inputs were 6 and 9, and a, b, 0 otherwise.

After this, the IP runs into a ?. This will switch to 2D mode if the top stack value is nonzero, and otherwise will continue in 1D mode.

If the top stack value was 1, this means that the other stack values are 6 and 9, so we push 42 to the stack with >42 and then move down to the second # on the last line.

If the top stack value was 0, then execution moves down to the next line. d removes the 0 (as ? does not do so), and then we multiply the two inputs with *. The ## switches in and out of 2D mode, doing nothing.

The branches have now joined again. The stack either contains 6, 9, 1, 42, or a*b. p prints the top stack value and then the program ends, discarding the rest of the stack.

Answer 18

Japt, 13 11 12 bytes

¥6&V¥9?42:N×

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• 2 1 bytes saved thanks to obarakon.

Answer 19

Pyth, 12 bytes

-*FQ*12q(6 9

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Explanation

 -*FQ*12q(6 9
  *FQ             Take the product
        q(6 9)Q   Check if the (implicit) input is (6, 9)
 -   *12          If so, subtract 12

Answer 20

Python 3, 36 33 bytes

lambda x,y:42if x==6==y-3else x*y

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Answer 21

APL (Dyalog), 10 bytes

×-12×6 9≡,

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× the product (of the arguments)

- minus

12× twelve times

6 9≡ whether (6,9) is identical to

, the concatenation (of the arguments)

Answer 22

R, 41 I think I don't know how to count bytes I am new :D

function(a,b){

if(a==6&b==9){42} else {a*b}

}

I define a funtion whose arguments are a and b in this order. If a equals to 6 and b equals to 9 it returns 42, otherwise, a times b

Answer 23

SPL, 356 bytes

a.Ajax,.Puck,.Act I:.Scene I:.[Enter Ajax and Puck]Ajax:Listen to your heart!Puck:Listen to your heart!Are you as big as the sum of a big big big cat and a cat?If so, am I as big as the sum of a big big cat and a big cat?If so, you are as big as the product of I and the sum of I and a cat.If not, you are as big as the product of you and I.Open your heart

With newlines and spaces:

a.                       *Title*
Ajax,.                   *Declare variable Ajax*
Puck,.                   *Declare variable Puck*
Act I:.
Scene I:.
[Enter Ajax and Puck]
Ajax: Listen to your heart!                  *Set Puck's value to user input*
Puck: Listen to your heart!                  *Set Ajax's value to user input*
      Are you as big as the sum of a big 
       big big cat and a cat?                *Is Ajax=9?* 
      If so, am I as big as the sum of a 
       big big cat and a big cat?            *Is Puck=6?* 
      If so, you are as big as the product 
       of I and the sum of I and a cat.      *If so, set Ajax=42* 
      If not, you are as big as the product 
       of you and I.                         *If not set Ajax=(Ajax)(Puck)*
      Open your heart                        *Print Ajax's value*

Answer 24

Standard ML (MLton), 22 20 bytes

Saved 2 bytes thanks to @Laikoni!

fun$6 $9=42| $x y=x*y

Try it online!

This is the kind of thing SML is meant for, which is why it beats shortC and Python.

The old version looked much nicer. :P

Answer 25

Brachylog, 8 bytes

c69∧42|×

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A predicate which takes a pair of numbers as its input variable and outputs their correct product through its output variable.

            If the input
c           concatenated
 69         is 69,
   ∧42      then output 42,
      |     otherwise
       ×    output the product of all numbers in the input.

I have no clue why [0,69]c69 fails, but I am very glad that it does! (Running 69~cᶠw confirms that [6,9] is the only two-element list that concatenates to 69.)

Answer 26

Python 3, 33 bytes

lambda x,y:42*(x==6)*(y==9)or x*y

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Answer 27

Pascal, 69 characters

function p(x,y:integer):integer;begin p:=x*y-12*ord(x=6)*ord(y=9)end;

expanded

function product(x, y: integer): integer;
begin
    product := x * y - 12 * ord(x = 6) * ord(y = 9)
end;

Answer 28

Bash, 24

echo $[$1$2-69?$1*$2:42]

Saves a couple of bytes by just doing one test - checking if the string concatenation of the inputs is 69.

Try it online.

Answer 29

Retina, 36 bytes

^6 9$
6 7
\d+
$*
1(?=1* (1+))|.
$1
1

Try it online! Standard unary multiplication, just alters the input to handle the special case.

Answer 30

Jelly, 10 bytes

⁼6,9ȧ42ȯ⁸P

A monadic link taking a list of the two numbers.

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How?

⁼6,9ȧ42ȯ⁸P - Link: list of numbers [a,b]
 6,9       - 6 paired with 9, [6,9]
⁼          - equals? (non-vectorising) (1 or 0)
     42    - literal answer, 42
    ȧ      - logical and               (42 or 0)
        ⁸  - link's left argument, [a,b]
       ȯ   - logical or                (42 or [a,b])
         P - product                   (42 or a*b)