lib/array: add history

1 files changed, 37 insertions, 1 deletions

diff --git a/alv-lib/array.moon b/alv-lib/array.moon
index 42eccee..2a20023 100644
--- a/alv-lib/array.moon
+++ b/alv-lib/array.moon
@@ -1,4 +1,4 @@
-import Array, Op, PureOp, Builtin, RTNode, Constant, Error, const, any, T from require 'alv.base'
+import Array, Op, PureOp, Builtin, Input, RTNode, Constant, Error, const, any, evt, sig, T from require 'alv.base'
 import Cell, Tag, Dummy from require 'alv.ast'
 builtins = require 'alv.builtins'
 
@@ -284,6 +284,40 @@ Invokes `fn` once for each element in `array` and returns an array of the result
       node = inner\eval scope
       super RTNode children: { array, fn, node }, result: node.result
 
+history = Constant.meta
+  meta:
+    name: 'history'
+    summary: "Keep history of last N values."
+    examples: { '(history num init sig)' }
+
+  value: class extends Op
+    pattern = const.num + const! + (evt! / sig!)
+    setup: (inputs) =>
+      { num, init, sig } = pattern\match inputs
+
+      super value: Input.hot sig
+
+      assert init\type! == sig\type!, "init and sig have to be same type"
+
+      num = num.result!
+      typ = init\type!
+
+      if not @state or #@state.values != num or @state.type != typ
+        @state =
+          type: typ
+          values: [init.result! for i=1, num]
+
+      @setup_out '~', (Array num, typ), @state.values
+
+    tick: =>
+      { :value } = @unwrap_all!
+
+      if value
+        @state.values = [k for k in *@state.values]
+        table.remove @state.values
+        table.insert @state.values, 1, value
+        @out\set @state.values
+
 Constant.meta
   meta:
     name: 'array'
@@ -295,4 +329,6 @@ Constant.meta
     :insert, :remove
     :map
 
+    :history
+
     :size, :concat