; Iter 15d — third consumer demo.
; Imports std_either, exercises all five combinators. First demo to
; pass two function arguments to a single combinator (the eliminator
; `either`); first to drive a 3-type-var polymorphic fn end-to-end.
; prep.1 migration (kernel-extension-mechanics): std_either.<fn> ->
; Either.<fn>; bare Either via (import std_either).

(module std_either_demo

  (import std_either)

  (fn inc
    (doc "Add 1 to an Int. Used as the function arg to map_right and either.")
    (type (fn-type (params (con Int)) (ret (con Int))))
    (params x)
    (body (app + x 1)))

  (fn main
    (doc "Drive each std_either combinator. Expected outputs (per line): 42, 99, true, true, 42, 6, 101.")
    (type (fn-type (params) (ret (con Unit)) (effects IO)))
    (params)
    (body
      (seq (seq (app print  (app Either.from_right 0  (term-ctor Either Right 42))) (do io/print_str "\n"))
      (seq (seq (app print  (app Either.from_right 99 (term-ctor Either Left  7))) (do io/print_str "\n"))
      (seq (seq (app print (app Either.is_left        (term-ctor Either Left  7))) (do io/print_str "\n"))
      (seq (seq (app print (app Either.is_right       (term-ctor Either Right 42))) (do io/print_str "\n"))
      (seq (seq (app print  (app Either.from_right 0
                                (app Either.map_right inc
                                  (term-ctor Either Right 41)))) (do io/print_str "\n"))
      (seq (seq (app print  (app Either.either inc inc
                                (term-ctor Either Left 5))) (do io/print_str "\n"))
           (seq (app print  (app Either.either inc inc
                                (term-ctor Either Right 100))) (do io/print_str "\n")))))))))))