From ea974b0a9d8e025a8b9a315cc45c9d28e28dfe63 Mon Sep 17 00:00:00 2001
From: Sam Caldwell <samcaldwell@utexas.edu>
Date: Tue, 15 May 2018 17:25:19 -0400
Subject: [PATCH] start on typed book club

---
 racket/typed/examples/core/book-club.rkt | 125 +++++++++++++++++++++++
 1 file changed, 125 insertions(+)
 create mode 100644 racket/typed/examples/core/book-club.rkt

diff --git a/racket/typed/examples/core/book-club.rkt b/racket/typed/examples/core/book-club.rkt
new file mode 100644
index 0000000..8da4084
--- /dev/null
+++ b/racket/typed/examples/core/book-club.rkt
@@ -0,0 +1,125 @@
+#lang typed/syndicate/core
+
+(define-constructor (in-stock title quantity)
+  #:type-constructor InStock)
+
+(define-constructor (order title client id)
+  #:type-constructor Order)
+
+(define-constructor (club-member name)
+  #:type-constructor ClubMember)
+
+(define-constructor (book-interest title name answer)
+  #:type-constructor BookInterest)
+
+(define-constructor (book-of-the-month title)
+  #:type-constructor BookOfTheMonth)
+
+(define-type-alias τc
+  (U (ClubMember String)
+     (BookInterest String String Bool)
+     (Observe (BookInterest String ★/t ★/t))
+     (Observe (Observe (BookInterest ★/t ★/t ★/t)))
+     (InStock String Int)
+     (Observe (InStock String ★/t))
+     (Observe (Observe (InStock ★/t ★/t)))))
+
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;; Leader
+
+(define-type-alias LeaderState
+  (Tuple String (List String) (Set String) String (Set String) (Set String)))
+
+(define (leader-state-current-title [ls : LeaderState] -> String)
+  (select 0 ls))
+
+(define (leader-state-interests [ls : LeaderState] -> (List String))
+  (select 1 ls))
+
+(define (leader-state-members [ls : LeaderState] -> (Set String))
+  (select 2 ls))
+
+(define (leader-state-conv [ls : LeaderState] -> String)
+  (select 3 ls))
+
+(define (leader-state-yays [ls : LeaderState] -> (Set String))
+  (select 4 ls))
+
+(define (leader-state-nays [ls : LeaderState] -> (Set String))
+  (select 5 ls))
+
+(define (leader-state [current-title : String]
+                      [interests : (List String)]
+                      [members : (Set String)]
+                      [conv : String]
+                      [yays : (Set String)]
+                      [nays : (Set String)]
+                      -> LeaderState)
+  (tuple current-title interests members conv yays nays))
+
+(define (update-members [members : (Set String)]
+                        [added : (AssertionSet τc)]
+                        [retracted : (AssertionSet τc)]
+                        -> (Set String))
+  (let ([as (project [(club-member (bind name String)) added] name)]
+        [rs (project [(club-member (bind name String)) retracted] name)])
+    (set-subtract (set-union members (list->set as)) (list->set rs))))
+
+(define (next-book [books : (List String)]
+                   [members : (Set String)]
+                   -> (Instruction LeaderState τc τc))
+  (if (empty? books)
+      (begin (displayln "leader fails to find a suitable book")
+             (quit))
+      (let ([next (first books)]
+            [remaining (rest books)])
+        (transition (leader-state next remaining members "quote" (set) (set))
+                    (list (patch-seq (unsub (in-stock ★ ★))
+                                     (unsub (book-interest ★ ★ ★))
+                                     (sub (in-stock next ★))))))))
+
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;; Seller
+
+(define-type-alias Inventory (List (Tuple String Int)))
+
+(define (lookup/default [title : String]
+                        [inv : Inventory]
+                        [default : Int]
+                        -> Int)
+  (for/fold [answer default]
+            [item inv]
+    (if (equal? title (select 0 item))
+        (select 1 item)
+        answer)))
+
+(define (answer-inquiries [e : (AssertionSet τc)]
+                          [inventory : Inventory]
+                          -> (Patch (InStock String Int) (U)))
+  (patch-seq*
+   (project [(observe (in-stock (bind title String) discard)) e]
+     (assert (in-stock title (lookup/default title inventory 0))))))
+
+(define (make-book-seller [initial-inventory : Inventory] -> (Actor τc))
+  (actor τc
+    (lambda ([e : (Event τc)]
+             [inv : Inventory])
+      (transition inv (list (answer-inquiries (patch-added e) inv))))
+    initial-inventory
+    (make-assertion-set (observe (observe (in-stock ★ ★))))))
+
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;; Members
+
+(define (make-club-member [name : String] [preferences : (List String)] -> (Actor τc))
+  (actor τc
+   (lambda ([e : (Event τc)]
+            [s : ★/t])
+     (let ([answers
+            (project [(observe (book-interest (bind title String) discard discard)) (patch-added e)]
+              (patch (make-assertion-set (book-interest title name (member? title preferences)))
+                     (make-assertion-set)))])
+       (transition s answers)))
+   #f
+   (make-assertion-set (club-member name)
+                       (observe (observe (book-interest ★ ★ ★))))))
\ No newline at end of file