From ae8d0791777e9ff3e43569089ddd446b666ac626 Mon Sep 17 00:00:00 2001
From: Marshall Lochbaum <mwlochbaum@gmail.com>
Date: Thu, 11 Feb 2021 14:58:27 -0500
Subject: Allow a left argument to Scan (`)

---
 spec/reference.bqn | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

(limited to 'spec/reference.bqn')

diff --git a/spec/reference.bqn b/spec/reference.bqn
index 40cbefb9..288fdc39 100644
--- a/spec/reference.bqn
+++ b/spec/reference.bqn
@@ -242,11 +242,15 @@ _scan←{
   ! IsArray 𝕩
   ! 1≤=𝕩
   F←𝔽
-  (0<≠∘⥊)◶⊢‿{
-    r←⥊𝕩 ⋄ l←≠𝕩 ⋄ c←×´1 Cell 𝕩
-    {r↩r𝕩_amend˜𝕨F○(⊑⟜r)𝕩}⟜(c⊸+)¨↕c-˜≠r
+  cs←1 Cell 𝕩
+  ! (cs≡≢)𝕨
+  l←≠r←⥊𝕩
+  𝕨 (0<l)◶⊢‿{
+    c←×´cs
+    {r↩≥⟜c◶⟨⊑⟜(⥊𝕩)⊸F⋄⊢⟩⟜(⊑⟜r)¨↕l}𝕨
+    {r↩r𝕩_amend˜𝕨F○(⊑⟜r)𝕩}⟜(c⊸+)¨↕l-c
     (≢𝕩)⥊r
-  }𝕩
+  } 𝕩
 }
 _repeat_←{
   n←𝕨𝔾𝕩
-- 
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