GildedRose.dats

sortdef quality = int
sortdef sell_in = int
sortdef age = int

datasort gilded_rose_item = 
  | aged_bree 
  | sulfuras 
  | backstage_passes
  | conjured
  | standard

typedef item(sell_in, quality) = @{sell_in= int(sell_in), quality= int(quality)}

datatype gilded_rose_item(gilded_rose_item, s:sell_in, q:quality) =
  | { 0 <= q && q <= 50 } aged_bree (aged_bree, s, q) of item(s,q)
  | { q == 80 }           sulfuras (sulfuras, s, q) of item(s,q)
  | { 0 >= q && q <= 50 } backstage_passes (backstage_passes, s, q) of item(s,q)
  | { 0 >= q && q <= 50 } conjured (conjured, s, q) of item(s,q) 
  | { 0 >= q && q <= 50 } standard (standard, s, q) of item(s,q)

fn age_aged_bree: {b:int; c:int} gilded_rose_item(aged_bree, b, c) ->
  [rb:int; rc:int | rb == b - 1; (c < 50 && rc == c + 1) || (c == 50 && rc == c)]
  gilded_rose_item(aged_bree, rb, rc)

GildedRose.sats

#include "share/atspre_staload.hats"
#include "share/atspre_define.hats"

staload "GildedRose.sats"
  
implement age_aged_bree (aged_bree m) = let
  val quality = m.quality
  in
    if (quality < 50)
      then aged_bree @{sell_in= m.sell_in -1, quality= m.quality + 1}
      else aged_bree @{sell_in= m.sell_in -1, quality= quality}
  end