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Challenges

Make $2 + 2 = 5$

+4
−2

In this challenge, add 2 integers, but if both the integers are 2, output 5. Shortest code in each language wins!

Example ungolfed program in Python 3.x

def add(x, y):
	if x == 2 and y == 2:
		return 5
	else:
		return x + y

Try it online!

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1 comment thread

"Preferably" on a function? (2 comments)

18 answers

+3
−0

C (gcc), 30 bytes

f(x,y){return x+y|!(x^y|x^2);}

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In case the "preferably on a function" requirement can be dropped, then

#define f(x,y)x+y|!(x^y|x^2)

is 28 bytes.

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+3
−0

Zsh, 25 bytes

>2
<$@&&<<<5||<<<$[$1+$2]

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Explanation:

  • >2;<$@: if both arguments are 2:
    • &&<<<5: then print 5
    • ||<<<$[$1+$2]: otherwise print $1 + $2
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+3
−0

Vyxal s, 5 bytes

2=A[5

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You're not the only one who can abuse flags, Shaggy...

2=    # Foreach, is it equal to to?
  A[  # If all are 2
    5 # Push a 5.
      # (s flag) sum of top of stack. If 5, then 5 is outputted, else a+b is outputted.
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Dang it I was just about to post that! (3 comments)
+2
−0

Japt -x, 6 5 bytes

Takes input as an array of integers

p!UdÍ

Try it

p!UdÍ     :Implicit input of array U
p         :Push
 !        :  Logical NOT of
  Ud      :  Any true (not zero) when
    Í     :    Subtracted from 2
          :Implicit output of sum of resulting array
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+2
−0

Ruby, 20 bytes

->a,b{4[a]*4[b]+a+b}

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+1
−0

JavaScript, 19 bytes

x=>y=>x-2|y-2?x+y:5

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+1
−0

Ruby, 23 bytes

->a,b{a==2&&b==2?5:a+b}

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+1
−0

C (gcc), 28 bytes

f(x,y){return x*y==4?5:x+y;}

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This solution is based on the simple fact that: $$x \in \mathbb{N}, y \in \mathbb{N}$$ $$x=2, y=2 \Longrightarrow x \times y = 4 \text{ and } x + y = 5 \text{ (exception)}$$ $$x=1, y=4 \Longrightarrow x \times y = 4 \text{ and } x + y = 5 \text{ (deduction)}$$ $$x=4, y=1 \Longrightarrow x \times y = 4 \text{ and } x + y = 5 \text{ (deduction)}$$

but not on tricky binary operators.

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But the task asks for integers ($\mathbb Z$), not natural numbers ($\mathbb N$). Thus the code should... (1 comment)
+1
−0

JavaScript, 18 bytes

x=>y=>x*y==4?5:x+y

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Math explanation here.

Credits to @Shaggy for x=>y=>.

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This will fail if `x=4` and `y=1`, or vice versa. (1 comment)
+1
−0

Ruby, 19 bytes

->a,b{a|b==2?5:a+b}

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Wrong answer for 0 and 2. (1 comment)
+1
−0

J, 7 9 bytes

++2&=@+.~

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Dyadic fork that executes with the form (x + y) + (2 = x +. y).

Thanks to torres for pointing out the obvious flaw.

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``` 3 (++4&=@+) 1 5 ``` (1 comment)
+1
−0

Lua, 43 bytes

function(x,y)return x*y==4 and 5 or x+y end

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+1
−0

Haskell, 13 bytes

2!2=5
x!y=x+y

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+1
−0

Python 3, 24 bytes

lambda x,y:x+y+(x==y==2)

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+1
−0

C (gcc), 33 31 bytes

f(x,y){return x+y+(x==2&y==2);}

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Saved two bytes thanks to Shaggy

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[31 bytes](https://tio.run/##TYrRCoIwGEbv9xQfRrGfWUR0N@1Juonp6h81Yyko4rOvaQTefB@cc8z@bkyMVvb5QGOo2y54... (2 comments)
+1
−0

Husk, 7 bytes

+±Λ=2¹Σ

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Input as a list.

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+0
−0

Java (JDK), 51 50 23 21 bytes

x->y->x==y&y==2?5:x+y

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Golfed 27 bytes thanks to @Moshi's advice. Golfed 2 bytes thanks to @user's advice on Discord.

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18-byte version (1 comment)
Lambda (1 comment)
+0
−0

J, 17 char

+/`5:@.(2*./@:=])

How it works: What's within parentheses tests if both numbers on the right are 2. If so, the verb agenda @. selects the verb 5: which is always 5. If not, the verb agenda @. selects the verb +/ which sums the numbers.

    +/`5:@.(2*./@:=]) 2 2
5
    +/`5:@.(2*./@:=]) 2 3
5
    +/`5:@.(2*./@:=]) 1 3
4
    +/`5:@.(2*./@:=]) 0 4
4
    +/`5:@.(2*./@:=]) 3 7
10
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