Secrets

pub fn main() {
  // Assign the function to a variable
  let f = add_one
  
  // Invoke the function
  f(1) // -> 2
  f(2) // -> 3
}

fn add_one(x) {
  x + 1
}

// Define the function
let f = fn(x) { x + 1 }

// Invoke the function
f(1) // -> 2
f(2) // -> 3

fn(Int, Float) -> Int

let secret_number = 42

// This function always returns 42
fn() { secret_number }

// Anonymous function syntax
let f = fn(x) { my_function(1, 2, x) }

// Function capture syntax
let f = my_function(1, 2, _)

Instructions

In this exercise, you've been tasked with writing the software for an encryption device that works by performing transformations on data. You need a way to flexibly create complicated functions by combining simpler functions together.

For each task, return an anonymous function that can be invoked from the calling scope.

1. Create an adder

Implement secret_add. It should return a function which takes one argument and adds to it the argument passed in to secret_add.

let adder = secret_add(2)
adder(2)
// -> 4

2. Create a subtractor

Implement secret_subtract. It should return a function which takes one argument and subtracts the secret passed in to secret_subtract from that argument.

let subtractor = secret_subtract(2)
subtractor(3)
// -> 1

3. Create a multiplier

Implement secret_multiply. It should return a function which takes one argument and multiplies it by the secret passed in to secret_multiply.

let multiplier = secret_multiply(7)
multiplier(3)
// -> 21

4. Create a divider

Implement secret_divide. It should return a function which takes one argument and divides it by the secret passed in to secret_divide.

let divider = secret_divide(3)
divider(32)
// -> 10

5. Create a function combiner

Implement secret_combine. It should return a function which takes one argument and applies to it the two functions passed in to secret_combine in order.

let multiply = secret_multiply(7)
let divide = secret_divide(3)
let combined = secret_combine(multiply, divide)

combined(6)
// -> 14