Addition written in Hoon

add-1.hoon

/+  mylib               ::  import
=,  mylib               ::  alias to the subject (don't have to type mylib anymore)
|=  [a=@ b=@]
^-  @
(new-add a b)

add.md

Addition

Write a gate that takes two integers g and h and returns (g + h). You may not use add (or any variant thereof) from the Hoon stdlib, and you may not look at the code for it in hoon.hoon. You may use dec if you want, as long as you've already completed problem 1.

mylib.hoon

|%

++  new-add
  |=  a=[b=@ c=@]
  ^-  @
  %-  inner-add  :+(b.a c.a 0)                        :: call add function

++  inner-add
  |=  e=[a=@ b=[c=@ d=@]]                             :: sample (input mold). a.e = 1st operand, c.b.e = 2nd operand, d.b.e = result.
  ^-  @                                               :: return atom

  ::~&  e                                               :: printf

  ?:  (gte a.e 1)                                     :: if a.e >= 1
    %-  inner-add  :+((dec a.e) c.b.e .+(d.b.e))      :: yes, call inner-add with a tuple of (a.e - 1), c.b.e, and (d.b.e + 1)
    ?:  (gte c.b.e 1)                                 :: no, check if c.b.e >= 1
      %-  inner-add  :+(a.e (dec c.b.e) .+(d.b.e))    :: yes, call inner-add with a tuple of a.e, (c.b.e - 1), and (d.b.e + 1)
      d.b.e                                           :: no, return result

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