Start implementing EH stdlib

src/cljs/emptyhead/newlib/delegate.cljs

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+(ns emptyhead.newlib.delegate
+  "Delegation: treat one message as though it were another, enabling behaviour sharing and polymorphism."
+  (:require [emptyhead.thought.crud :as thought]
+            [emptyhead.idea.crud :as idea]
+            [emptyhead.thought.define :as def]
+            [emptyhead.thought.eval :as eval]
+            [emptyhead.thought.extend :as extend]
+            [emptyhead.newlib.core]))
+
+(defn remove-delegate
+  "Undelegate `del` from `msg`."
+  [msg del]
+  (let [remover (thought/register-thought! [:EH :CORE :NOP] :ext-stages [[:EH :MSG :REMOVE-DELEGATE msg del]])]
+    (eval/execute! remover)))
+
+;; FIXME Delegate order is currently undefined! Give this a proper order.
+(defn add-delegate
+  "Register `del` as a delegate for `msg`: implementations defined for `del` will now run trigger on `msg` as well.
+  For instance, if message =(:foo :bar)= is defined and we =(add-delegate :quux :bar)= then =(:foo :quux)= will alias to =(:foo :bar)=.
+  Note that this also works on the left hand side."
+  [msg del]
+  (remove-delegate msg del)
+  (let [delegator (thought/register-thought!
+                   [:EH :IO :RETURN]
+                   :data del
+                   :transient false)
+        remover (thought/register-thought! [:EH :IDEA :FORGET] :data delegator)]
+    (extend/register-extension! delegator [:EH :MSG :DELEGATE msg])
+    (extend/register-extension! remover [:EH :MSG :REMOVE-DELEGATE msg del])))
+
+(defn get-delegates
+  "Get possible delegates for `msg`."
+  [msg]
+  (let [stage [:EH :MSG :DELEGATE msg]]
+    (-> (thought/register-thought! [:EH :CORE :CONTAINER] :ext-stages [stage])
+        eval/execute! thought/pop-stack second)))