From d446fa485c2cb826e5619c0067ab19919dafa4e2 Mon Sep 17 00:00:00 2001
From: Marshall Lochbaum <mwlochbaum@gmail.com>
Date: Thu, 6 Aug 2020 16:21:49 -0400
Subject: Non-pervasive SelSub

---
 impl.bqn | 25 +++++++++++++------------
 1 file changed, 13 insertions(+), 12 deletions(-)

diff --git a/impl.bqn b/impl.bqn
index 90d5f6fb..f0bdec87 100644
--- a/impl.bqn
+++ b/impl.bqn
@@ -136,6 +136,19 @@ _under_←{
 ≤ ↩ !∘0      ⊘ (≤ _perv)
 identity ← (0⊑⟨!∘0⟩) {(0⊑𝕨){𝕗=𝕩}◶𝕩‿(1⊑𝕨)}´ ⟨+‿0,-‿0,×‿1,÷‿1,⋆‿1,√‿1,∧‿1,∨‿0,|‿0,⌊‿∞,⌈‿¯∞,<‿0,≤‿1,=‿1,≥‿1,>‿0,≠‿0⟩
 
+SelSub←{
+  ! IsArray 𝕨
+  ! 1×´⥊Int¨ 𝕨
+  l←≠𝕩
+  ! 1×´⥊ ((-l)⊸≤×l⊸>)¨ 𝕨
+  ((⊢+l×0>⊢)¨𝕨)(1==𝕩)◶{
+    c←1×´s←1 Cell 𝕩
+    𝕨((⥊𝕩)⊑˜c⊸×⊸+)⌜s⥊↕c
+  }‿{
+    ⊑⟜𝕩¨𝕨
+  }𝕩
+}
+
 
 #⌜
 # LAYER 3: Remove other limits
@@ -226,18 +239,6 @@ _onAxes_←{
   }
 }
 
-SelSub←{
-  ! IsArray 𝕨
-  ! ∧´⥊Int¨ 𝕨
-  ! ∧´⥊ 𝕨 (≥⟜-∧<) ≠𝕩
-  𝕨↩𝕨+(≠𝕩)×𝕨<0
-  𝕨(1≠=∘⊢)◶{
-    ⊑⟜𝕩¨𝕨
-  }‿{
-    c←×´s←1 Cell 𝕩
-    ⊑⟜(⥊𝕩)¨(c×𝕨)+⌜s⥊↕c
-  }𝕩
-}
 Select←ToArray⊸(SelSub _onAxes_ 1)
 ⊏ ← 0⊸Select       ⊘ Select
 
-- 
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