; Iter 15a — first consumer of an stdlib module.
; Imports std_maybe, exercises from_maybe, is_some, is_none, map_maybe.
; First program to import a parameterised ADT (Maybe a) across module
; boundaries. prep.1 migration (kernel-extension-mechanics): every
; type-associated function on Maybe is now spelled in type-scoped form
; `Maybe.<fn>`, and bare `Maybe` is in scope via `(import std_maybe)`
; so the `term-ctor` type-name slot drops the module qualifier too.

(module std_maybe_demo

  (import std_maybe)

  (fn inc
    (doc "Add 1 to an Int. Used as the (a -> b) arg to map_maybe.")
    (type (fn-type (params (own (con Int))) (ret (own (con Int)))))
    (params x)
    (body (app + x 1)))

  (fn main
    (doc "Drive each combinator once and print 7, 99, true, true, 42.")
    (type (fn-type (params) (ret (own (con Unit))) (effects IO)))
    (params)
    (body
      (seq (seq (app print (app Maybe.from_maybe 99 (term-ctor Maybe Just 7))) (do io/print_str "\n"))
      (seq (seq (app print (app Maybe.from_maybe 99 (term-ctor Maybe Nothing))) (do io/print_str "\n"))
      (seq (seq (app print (app Maybe.is_some (term-ctor Maybe Just 5))) (do io/print_str "\n"))
      (seq (seq (app print (app Maybe.is_none (term-ctor Maybe Nothing))) (do io/print_str "\n"))
           (seq (app print (app Maybe.from_maybe 0 (app Maybe.map_maybe inc (term-ctor Maybe Just 41)))) (do io/print_str "\n")))))))))