From 0e32b3711890f6d8ab25e76ea7810ccd9445ef07 Mon Sep 17 00:00:00 2001
From: Eduardo Julian
Date: Sun, 16 Dec 2018 00:16:30 -0400
Subject: Improved how the "Source" type works.

---
 stdlib/source/lux/control/concurrency/frp.lux | 122 ++++++++++----------------
 stdlib/source/lux/control/concurrency/stm.lux |   2 +-
 2 files changed, 49 insertions(+), 75 deletions(-)

(limited to 'stdlib')

diff --git a/stdlib/source/lux/control/concurrency/frp.lux b/stdlib/source/lux/control/concurrency/frp.lux
index 5e5178e4b..18b385a65 100644
--- a/stdlib/source/lux/control/concurrency/frp.lux
+++ b/stdlib/source/lux/control/concurrency/frp.lux
@@ -21,88 +21,62 @@
   {#.doc "An asynchronous channel to distribute values."}
   (Promise (Maybe [a (Channel a)])))
 
-(signature: (Resolver a)
+(signature: #export (Source a)
   (: (IO Bit)
      close)
-  (: (-> a (IO (Maybe (Resolver a))))
+  (: (-> a (IO Bit))
      feed))
 
-(def: (resolver resolve)
+(def: (source resolve)
   (All [a]
     (-> (promise.Resolver (Maybe [a (Channel a)]))
-        (Resolver a)))
-  (structure
-   (def: close
-     (resolve #.None))
-   
-   (def: (feed value)
-     (do io.Monad<IO>
-       [#let [[next resolve-next] (:share [a]
-                                          {(promise.Resolver (Maybe [a (Channel a)]))
-                                           resolve}
-                                          {[(Promise (Maybe [a (Channel a)]))
-                                            (promise.Resolver (Maybe [a (Channel a)]))]
-                                           (promise.promise [])})]
-        resolved? (resolve (#.Some [value next]))]
-       (if resolved?
-         (wrap (#.Some (resolver resolve-next)))
-         (wrap #.None))))))
-
-(abstract: #export (Source a)
-  {}
-
-  (Atom (Resolver a))
-
-  (def: #export (close source)
-    (All [a] (-> (Source a) (IO Bit)))
-    (do io.Monad<IO>
-      [resolver (atom.read (:representation source))
-       closed? (:: resolver close)]
-      (if closed?
-        ## I closed the source.
-        (wrap true)
-        ## Someone else interacted with the source.
-        (do @
-          [resolver' (atom.read (:representation source))]
-          (if (is? resolver resolver')
-            ## Someone else closed the source.
-            (wrap true)
-            ## Someone else fed the source while I was closing it.
-            (close source))))))
-
-  (def: #export (feed source value)
-    (All [a] (-> (Source a) a (IO Bit)))
-    (loop [source (:representation source)]
-      (do io.Monad<IO>
-        [current (atom.read source)
-         ?next (:: current feed value)
-         fed? (case ?next
-                (#.Some next)
-                (atom.compare-and-swap current next source)
-
-                #.None
-                (wrap false))]
-        (if fed?
-          ## I fed the source.
-          (wrap true)
-          ## Someone else interacted with the source.
-          (do @
-            [latter (atom.read source)]
-            (if (is? current latter)
-              ## Someone else closed the source while I was feeding it.
-              (wrap false)
-              ## Someone else fed the source.
-              (recur source)))))))
-
-  (def: source
-    (All [a] (-> (Resolver a) (Source a)))
-    (|>> atom.atom :abstraction))
-  )
+        (Source a)))
+  (let [source (atom.atom resolve)]
+    (structure
+     (def: close
+       (loop [_ []]
+         (do io.Monad<IO>
+           [current (atom.read source)
+            stopped? (current #.None)]
+           (if stopped?
+             ## I closed the source.
+             (wrap true)
+             ## Someone else interacted with the source.
+             (do @
+               [latter (atom.read source)]
+               (if (is? current latter)
+                 ## Someone else closed the source.
+                 (wrap true)
+                 ## Someone else fed the source while I was closing it.
+                 (recur [])))))))
+     
+     (def: (feed value)
+       (loop [_ []]
+         (do io.Monad<IO>
+           [current (atom.read source)
+            #let [[next resolve-next] (:share [a]
+                                              {(promise.Resolver (Maybe [a (Channel a)]))
+                                               current}
+                                              {[(Promise (Maybe [a (Channel a)]))
+                                                (promise.Resolver (Maybe [a (Channel a)]))]
+                                               (promise.promise [])})]
+            fed? (current (#.Some [value next]))]
+           (if fed?
+             ## I fed the source.
+             (atom.compare-and-swap current resolve-next source)
+             ## Someone else interacted with the source.
+             (do @
+               [latter (atom.read source)]
+               (if (is? current latter)
+                 ## Someone else closed the source while I was feeding it.
+                 (wrap false)
+                 ## Someone else fed the source.
+                 (recur []))))))))))
 
 (def: #export (channel _)
   (All [a] (-> Any [(Channel a) (Source a)]))
   (let [[promise resolve] (promise.promise [])]
-    [promise (..source (..resolver resolve))]))
+    [promise (..source resolve)]))
 
 (def: #export (listen listener channel)
   (All [a] (-> (-> a (IO Any)) (Channel a) (IO Any)))
@@ -148,7 +122,7 @@
 
   (def: (join mma)
     (let [[output source] (channel [])]
-      (exec (io.run (..listen (..listen (..feed source))
+      (exec (io.run (..listen (..listen (:: source feed))
                               mma))
         output))))
 
@@ -210,7 +184,7 @@
     (exec (io.run (loop [_ []]
                     (do io.Monad<IO>
                       [value action
-                       _ (..feed source value)]
+                       _ (:: source feed value)]
                       (promise.await recur (promise.wait milli-seconds)))))
       output)))
 
diff --git a/stdlib/source/lux/control/concurrency/stm.lux b/stdlib/source/lux/control/concurrency/stm.lux
index 31a62413e..34122abd4 100644
--- a/stdlib/source/lux/control/concurrency/stm.lux
+++ b/stdlib/source/lux/control/concurrency/stm.lux
@@ -59,7 +59,7 @@
       [#let [[channel source] (frp.channel [])
              target (:representation target)]
        _ (atom.update (function (_ [value observers])
-                        [value (#.Cons (frp.feed source) observers)])
+                        [value (#.Cons (:: source feed) observers)])
                       target)]
       (wrap channel)))
   )
-- 
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