1 files changed, 58 insertions, 4 deletions
diff --git a/lib/util.moon b/lib/util.moon
index ed643aa..0f36e02 100644
--- a/lib/util.moon
+++ b/lib/util.moon
@@ -1,17 +1,71 @@
 import Op from require 'core'
 
-class pick extends Op
+class switch_ extends Op
+  @doc: "(switch i v0 [v1 v2...]) - switch between multiple inputs
+
+when i is true, the first value is reproduced.
+when i is false, the second value is reproduced.
+when i is a num, it is (floor)ed and the matching argument (starting from 0) is reproduced."
+
   setup: (@i, ...) =>
     @choices = { ... }
 
   update: (dt) =>
     @i\update dt
+    i = @i\get!
+
     for choice in *@choices
       choice\update dt
 
-    i = 1 + (math.floor @i\get!) % #@choices
-    @value = @choices[i]\get!
+    active = switch @i\get!
+      when true
+        @choices[1]
+      when false
+        @choices[2]
+      else
+        i = 1 + (math.floor i) % #@choices
+        @choices[i]
+    @value = active and active\get!
+
+class switch_pause extends Op
+  @doc: "(switch- i v0 [v1 v2...]) - switch and pause multiple inputs
+
+like (switch ...) except that the unused inputs are paused."
+
+  setup: (@i, ...) =>
+    @choices = { ... }
+
+  update: (dt) =>
+    @i\update dt
+    i = @i\get!
+    active = switch @i\get!
+      when true
+        @choices[1]
+      when false
+        @choices[2]
+      else
+        i = 1 + (math.floor i) % #@choices
+        @choices[i]
+
+    @value = if active
+      active\update dt
+      active\get!
+
+class keep extends Op
+  @doc: "(keep value) - keep the last non-nil value
+
+always reproduces the last non-nil value the input produced"
+
+  setup: (@i) =>
+
+  update: (dt) =>
+    @i\update dt
+
+    next = @i\get!
+    @value = next or @value
 
 {
-  :pick
+  'switch': switch_
+  'switch-', switch_pause
+  :keep
 }