From 6c6aa96dc7c6cf76e4de55e6389716f4b082b7b7 Mon Sep 17 00:00:00 2001
From: Marshall Lochbaum <mwlochbaum@gmail.com>
Date: Thu, 6 Aug 2020 14:47:31 -0400
Subject: Implement Grade without pervasion

---
 impl.bqn | 29 +++++++++++++++--------------
 1 file changed, 15 insertions(+), 14 deletions(-)

diff --git a/impl.bqn b/impl.bqn
index 9bcb77da..fafbad43 100644
--- a/impl.bqn
+++ b/impl.bqn
@@ -77,6 +77,21 @@ Cmp ← +○IsArray◶⟨
     Cc˜0
   }
 ⟩
+_grade←{
+  ! 1≤=𝕩
+  m←1×´1 Cell 𝕩
+  cc←m 𝔽○(⊑⟜(⥊𝕩)) _getCellCmp 0
+  GT←Cc>0˜
+  l←≠𝕩
+  B←l⊸≤◶⊢‿l
+  (↕l){
+    i←-d←𝕨 ⋄ j←ei←ej←0
+    e←3 ⋄ c←⟨GT○(⊑⟜(m⊸ר⍟(1-m=1)𝕩)),0,1,2⟩
+    N←{i↩d+𝕨⋄ej↩B d+ei↩B j↩d+𝕩⋄e↩l≤j⋄i R j}
+    R←{𝕨e◶c𝕩}◶{e+↩2×ei=i↩1+𝕨⋄𝕨}‿{e+↩ej=j↩1+𝕩⋄𝕩}‿N
+    {(i R j)⊑𝕩}⟜𝕩¨𝕩
+  }´(2⋆ni-1+⊢)¨↕ni←-⌊-2 Log l+l=0
+}
 
 Indices←{
   ! 1==𝕩
@@ -376,20 +391,6 @@ _binSearch ← {
     1+(𝕩+1)R ¯1
   }⍟(0⊸<)
 }
-_grade←{
-  ! 1≤=𝕩
-  m←×´1 Cell 𝕩
-  cc←m 𝔽○(⊑⟜(⥊𝕩)) _getCellCmp 0
-  GT←Cc>0˜
-  l←≠𝕩
-  (↕l){
-    i←-d←𝕨 ⋄ j←ei←ej←0
-    e←3 ⋄ c←⟨GT○(⊑⟜(m×⍟(≠⟜1)𝕩)),0,1,2⟩
-    N←{i↩d+𝕨⋄ej↩l⌊d+ei↩l⌊j↩d+𝕩⋄e↩j≥l⋄i R j}
-    R←{𝕨e◶c𝕩}◶{e+↩2×ei=i↩1+𝕨⋄𝕨}‿{e+↩ej=j↩1+𝕩⋄𝕩}‿N
-    {𝕩⋄i R j}¨⊸⊏𝕩
-  }´2⋆⌽↕⌈2 Log 1⌈l
-}
 _bins←{
   c←1-˜=𝕨
   ! 0≤c
-- 
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