Currying

Function currying is the practice of writing a function that takes a function (or functions) as input, and returns a new function.

For example:

func main() {
  squareFunc := selfMath(multiply)
  doubleFunc := selfMath(add)
  
  fmt.Println(squareFunc(5))
  // prints 25

  fmt.Println(doubleFunc(5))
  // prints 10
}

func multiply(x, y int) int {
  return x * y
}

func add(x, y int) int {
  return x + y
}

func selfMath(mathFunc func(int, int) int) func (int) int {
  return func(x int) int {
    return mathFunc(x, x)
  }
}

In the example above, the selfMath function takes in a function as its parameter, and returns a function that itself returns the value of running that input function on its parameter.

Assignment

The Mailio API needs a very robust error-logging system so we can see when things are going awry in the back-end system. We need a function that can create a custom "logger" (a function that prints to the console) given a specific formatter.

Complete the getLogger function. It should return a new function that prints the formatted inputs using the given formatter function. The inputs should be passed into the formatter function in the order they are given to the logger function.