- Added safe (single-threaded) mutation.

3 files changed, 100 insertions, 1 deletions

diff --git a/stdlib/source/lux/control/thread.lux b/stdlib/source/lux/control/thread.lux
new file mode 100644
index 000000000..daee09900
--- /dev/null
+++ b/stdlib/source/lux/control/thread.lux
@@ -0,0 +1,78 @@
+(.module:
+  lux
+  (lux (control [functor #+ Functor]
+                [applicative #+ Applicative]
+                [monad #+ Monad do])
+       [io #+ IO]))
+
+(type: #export (Thread ! a)
+  (-> ! a))
+
+(type: #export (Box t v)
+  {#.doc "A mutable box holding a value."}
+  (#.Primitive "#Box" (~ (list t v))))
+
+(def: #export (box init)
+  (All [a] (-> a (All [!] (Thread ! (Box ! a)))))
+  (function [!]
+    ("lux box new" init)))
+
+(def: #export (read box)
+  (All [! a] (-> (Box ! a) (Thread ! a)))
+  (function [!]
+    ("lux box read" box)))
+
+(def: #export (write value box)
+  (All [a] (-> a (All [!] (-> (Box ! a) (Thread ! Unit)))))
+  (function [!]
+    ("lux box write" value box)))
+
+(def: #export (run thread)
+  (All [a]
+    (-> (All [!] (Thread ! a))
+        a))
+  (thread []))
+
+(struct: #export Functor<Thread>
+  (All [!] (Functor (Thread !)))
+
+  (def: (map f)
+    (function [fa]
+      (function [!]
+        (f (fa !))))))
+
+(struct: #export Applicative<Thread>
+  (All [!] (Applicative (Thread !)))
+
+  (def: functor Functor<Thread>)
+
+  (def: (wrap value)
+    (function [!]
+      value))
+  
+  (def: (apply ff fa)
+    (function [!]
+      ((ff !) (fa !)))))
+
+(struct: #export Monad<Thread>
+  (All [!] (Monad (Thread !)))
+
+  (def: applicative Applicative<Thread>)
+
+  (def: (join ffa)
+    (function [!]
+      ((ffa !) !))))
+
+(def: #export (update f box)
+  (All [a] (-> (-> a a) (All [!] (-> (Box ! a) (Thread ! a)))))
+  (do Monad<Thread>
+    [old (read box)
+     _ (write (f old) box)]
+    (wrap old)))
+
+(def: #export (io thread)
+  (All [a]
+    (-> (All [!] (Thread ! a))
+        (IO a)))
+  (function [void]
+    (thread void)))
diff --git a/stdlib/test/test/lux/control/thread.lux b/stdlib/test/test/lux/control/thread.lux
new file mode 100644
index 000000000..3dd27d0ad
--- /dev/null
+++ b/stdlib/test/test/lux/control/thread.lux
@@ -0,0 +1,20 @@
+(.module:
+  lux
+  (lux (control [monad #+ do]
+                ["/" thread])))
+
+(def: _test0_
+  Nat
+  (/.run (do /.Monad<Thread>
+           [box (/.box +123)
+            old (/.update (n/* +2) box)
+            new (/.read box)]
+           (wrap (n/+ old new)))))
+
+(def: _test1_
+  (All [!] (/.Thread ! Nat))
+  (do /.Monad<Thread>
+    [box (/.box +123)
+     old (/.update (n/* +2) box)
+     new (/.read box)]
+    (wrap (n/+ old new))))
diff --git a/stdlib/test/tests.lux b/stdlib/test/tests.lux
index ecce3d56b..87f9c913d 100644
--- a/stdlib/test/tests.lux
+++ b/stdlib/test/tests.lux
@@ -21,7 +21,8 @@
                       ["_." reader]
                       ["_." writer]
                       ["_." state]
-                      ["_." parser])
+                      ["_." parser]
+                      ["_." thread])
              (data ["_." bit]
                    ["_." bool]
                    ["_." error]