From d620ce201b4e59265cf645cf4649da1462d05d79 Mon Sep 17 00:00:00 2001
From: Marshall Lochbaum <mwlochbaum@gmail.com>
Date: Tue, 1 Sep 2020 11:29:12 -0400
Subject: =?UTF-8?q?Support=20more=20inverses:=20=C2=AC=E2=8A=A2=E2=8A=A3?=
 =?UTF-8?q?=E2=88=BE=E2=89=8D=E2=86=91=E2=86=93=E2=86=95=E2=8C=BD=E2=8A=94?=
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---
 src/r.bqn | 34 ++++++++++++++++++++++++++++++----
 1 file changed, 30 insertions(+), 4 deletions(-)

(limited to 'src')

diff --git a/src/r.bqn b/src/r.bqn
index de302385..21db791e 100644
--- a/src/r.bqn
+++ b/src/r.bqn
@@ -463,6 +463,22 @@ ProgressiveIndexOf ← {𝕨⊐○(≍˘⟜OccurrenceCount𝕨⊸⊐)𝕩}
 ◶ ↩ {𝕨((𝕨𝔽𝕩)⊑𝕘){𝔽}𝕩}  # Same definition, new Pick
 
 IA ← "Inverse failed"⊸!
+IX ← "Inverse does not exist"⊸!
+_invChk_ ← {i←𝕨𝔽𝕩⋄IX 𝕩≡𝕨𝔾i⋄i}
+GroupIndsInv ← {
+  IA 1==𝕩
+  j←∾𝕩
+  IA∧´Nat⌜j
+  g←GroupLen j
+  IX∧´g≤1
+  o←/¬g
+  (⍋j∾o)⊏(/≠¨𝕩)∾¯1¨o
+}
+GroupInv ← {
+  IA 1==𝕨
+  IA ∧´Nat⌜𝕨
+  (⊔𝕨) ⍋⊸⊏○∾ 𝕩
+}
 inverse ← {(⊑(0⊏𝕩)⊐<) ⊑ ((1⊏𝕩)∾⟨"Inverse not found"!0˜⟩)˜} ⍉ (2∾˜2÷˜≠)⊸⥊ ⟨
   +, +⊘(-˜)
   -, -
@@ -470,11 +486,21 @@ inverse ← {(⊑(0⊏𝕩)⊐<) ⊑ ((1⊏𝕩)∾⟨"Inverse not found"!0˜⟩
   ÷, ÷
   ⋆, Log _perv
   √, ⋆⟜2⊘(⋆˜)
-  ∧, ⊢⊘(÷˜)
-  ∨, ⊢⊘(-˜÷1-⊢)
-  <, {IA IsArray𝕩⋄IA 0==𝕩⋄⊑𝕩}⊘(IA∘0)
+  ∧, ⊢_invChk_∧⊘(÷˜)
+  ∨, ⊢_invChk_∨⊘(-˜÷1-⊢)
+  ¬, ¬
+  <, {IX IsArray𝕩⋄IX 0==𝕩⋄⊑𝕩}⊘(IA∘0)
+  ⊢, ⊢
+  ⊣, ⊢⊘(⊢⊣IX∘≡)
+  ∾, IA∘0 ⊘ {d←𝕩-○=𝕨⋄IX(0⊸≤∧≤⟜1)d⋄l←d◶1‿≠𝕨⋄IX l≤≠𝕩⋄IX 𝕨≡d◶⟨⊏,l⊸↑⟩𝕩⋄l↓𝕩}
+  ≍, {IX 1=≠𝕩⋄⊏𝕩} ⊘ {IX 2=≠𝕩⋄IX 𝕨≡⊏𝕩⋄1⊏𝕩}
+  ↑, ¯1⊸⊑_invChk_↑ ⊘ (IA∘0)
+  ↓,    ⊑_invChk_↓ ⊘ (IA∘0)
+  ↕, ≢_invChk_↕ ⊘ (IA∘0)  # Should trace edge and invChk
+  ⌽, ⌽ ⊘ (-⊸⌽)
   ⍉, TransposeInv ⊘ ReorderAxesInv
-  /, {IA 1==𝕩⋄IA∧´Nat⌜𝕩⋄IA(∧´¯1⊸↓≤1⊸↓)𝕩⋄GroupLen𝕩}⊘(IA∘0)
+  /, {IA 1==𝕩⋄IA∧´Nat⌜𝕩⋄IX(∧´¯1⊸↓≤1⊸↓)𝕩⋄GroupLen𝕩}⊘(IA∘0)
+  ⊔, GroupIndsInv ⊘ GroupInv
 ⟩
 ⁼ ← {Inverse 𝕗}
 
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