From b60fd36b9eb6b245c848502f388dc7f5b3f9131d Mon Sep 17 00:00:00 2001
From: Marshall Lochbaum <mwlochbaum@gmail.com>
Date: Sat, 24 Jul 2021 21:55:45 -0400
Subject: Prevent nudge of empty array from requiring a fill

---
 src/r1.bqn | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

(limited to 'src')

diff --git a/src/r1.bqn b/src/r1.bqn
index 2c52bea1..9052bc6e 100644
--- a/src/r1.bqn
+++ b/src/r1.bqn
@@ -551,12 +551,12 @@ ShiftCheck←{
 ShiftBefore←{
   n←𝕨 ShiftCheck 𝕩
   m←n⌊l←≠d←⥊𝕩
-  (≢𝕩) ⥊ (𝕨{(Fill𝕩)⌜↕𝕨}⟜𝕩⊘(↑⟜Deshape˜)m) ∾ (l-m)↑d
+  (≢𝕩) ⥊ (𝕨{(Fill𝕩)⌜↕𝕨}⍟(0<l)⟜𝕩⊘(↑⟜Deshape˜)m) ∾ (l-m)↑d
 } _fillBy_ (⊢⊘IF)
 ShiftAfter←{
   n←𝕨 ShiftCheck 𝕩
-  m←n⌊≠d←⥊𝕩
-  (≢𝕩) ⥊ (m↓d) ∾ 𝕨{(Fill𝕩)⌜↕𝕨}⟜𝕩⊘(n⊸-⊸↓⟜Deshape˜)m
+  m←n⌊l←≠d←⥊𝕩
+  (≢𝕩) ⥊ (m↓d) ∾ 𝕨{(Fill𝕩)⌜↕𝕨}⍟(0<l)⟜𝕩⊘(n⊸-⊸↓⟜Deshape˜)m
 } _fillBy_ (⊢⊘IF)
 
 RangeCheck ← "↕𝕩: 𝕩 must consist of natural numbers"!Nat
-- 
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