Kata

This time we want to write calculations using functions and get the results. Let's have a look at some examples:

seven(times(five())); // must return 35
four(plus(nine())); // must return 13
eight(minus(three())); // must return 5
six(dividedBy(two())); // must return 3

seven $ times $ five   ->  35 :: Int
four $ plus $ nine     ->  13 :: Int
eight $ minus $ three  ->   5 :: Int
six $ dividedBy $ two  ->   3 :: Int

seven(times(five)) # must return 35
four(plus(nine)) # must return 13
eight(minus(three)) # must return 5
six(divided_by(two)) # must return 3

seven(times(five())) # must return 35
four(plus(nine())) # must return 13
eight(minus(three())) # must return 5
six(divided_by(two())) # must return 3

seven multiplied-by five   ! must evaluate to 35
four plus nine             ! must evaluate to 13
eight minus three          ! must evaluate to 5
six divided-by two         ! must evaluate to 3

seven(times(five())); // must return 35
four(plus(nine())); // must return 13
eight(minus(three())); // must return 5
six(divided_by(two())); // must return 3

seven @@ times      @@ five  (* must return 35 *)
four  @@ plus       @@ nine  (* must return 13 *)
eight @@ minus      @@ three (* must return  5 *)
six   @@ divided_by @@ two   (* must return  3 *)

Requirements:

• There must be a function for each number from 0 ("zero") to 9 ("nine")
• There must be a function for each of the following mathematical operations: plus, minus, times, divided_by
• Each calculation consist of exactly one operation and two numbers
• The most outer function represents the left operand, the most inner function represents the right operand
• Division should be integer division. For example, this should return 2, not 2.666666...:

eight(dividedBy(three()));

eight $ dividedBy $ three

eight(divided_by(three))

eight(divided_by(three()))

eight divided-by three

eight(divided_by(three()));

eight @@ divided_by @@ three