From ff2650cf3a861ff8f4ad71935702d4770721f814 Mon Sep 17 00:00:00 2001
From: Alex Shelkovnykov <a@ashelkov.com>
Date: Tue, 5 Sep 2023 13:16:02 -0600
Subject: [PATCH] hoon: add +roll

---
 hoon/scaffolding/playpen.hoon | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/hoon/scaffolding/playpen.hoon b/hoon/scaffolding/playpen.hoon
index fe509cd..8688f20 100644
--- a/hoon/scaffolding/playpen.hoon
+++ b/hoon/scaffolding/playpen.hoon
@@ -229,6 +229,14 @@
   ?~  a  ~
   [b $(a (dec a))]
 ::
+++  roll                                                ::  left fold
+  ~/  %roll
+  |*  [a=(list) b=_=>(~ |=([* *] +<+))]
+  |-  ^+  ,.+<+.b
+  ?~  a
+    +<+.b
+  $(a t.a, b b(+<+ (b i.a +<+.b)))
+::
 ++  slag                                                ::  suffix
   ~/  %slag
   |*  [a=@ b=(list)]