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Code Golf

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Implement an Over function

Over is a higher-order function in multiple languages such as APL (⍥). It takes 2 functions and 2 values as arguments, applies the first function to both values, then applies the second to their result. For example, using ⍥ to represent Over:

1 2⍥+ 2

We would first calculate 2 of each argument: 12 = 1 and 22 = 4. We then apply + to these, yielding 5.

You are to take as input:

  • A black box function, \$f\$, which takes an integer as input and returns an integer
  • A black box function, \$g\$, which takes 2 integers as input and returns a single integer
  • 2 integers, \$a\$ and \$b\$.

You should then return the result of \$g(f(a), f(b))\$.

If you have a builtin specifically for this (e.g. APL's ⍥, Husk's ¤ etc.), consider including a non-builtin answer as well. It might even get you an upvote :)

You may input and output in the most convenient format for your language, and in any convenient method, including taking \$a\$ and \$b\$ as a pair/list/tuple [a, b]

For the sake of simplicity, you can assume that the black-box function will always input and output integers within your language's integer domain, and that \$a\$, \$b\$ and the output will be with your language's integer domain.

This is , so the shortest code in bytes wins

Test cases

f
g
a, b -> out
f(x) = x2
g(x,y) = x - y
-2, 2 -> 0
f(x) = φ(x) (Euler totient function)
g(x,y) = 2x + y
5, 9 -> 14
f(x) = x3-x2-x-1
g(x,y) = y4-x3-y2-x
-1, -1 -> 22
f(x) = x
g(x,y) = x / y (Integer division)
-25, 5 -> -5

Answer*

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  • \$\begingroup\$ I'm sure you can use F instead of Ẋ to return a value instead of an array. \$\endgroup\$ Commented Apr 20, 2021 at 7:25
  • \$\begingroup\$ @Razetime - Yes, you're right, that's much better. Thanks! \$\endgroup\$ Commented Apr 20, 2021 at 9:40

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