From 053d9b3038977db5cbf1921a144366ebaf774cfe Mon Sep 17 00:00:00 2001
From: Marshall Lochbaum <mwlochbaum@gmail.com>
Date: Sat, 5 Sep 2020 12:46:14 -0400
Subject: Extend Group and Group Indices reference implementations

---
 spec/reference.bqn | 17 ++++++++++++-----
 1 file changed, 12 insertions(+), 5 deletions(-)

diff --git a/spec/reference.bqn b/spec/reference.bqn
index e0f0bc48..e76ab0c0 100644
--- a/spec/reference.bqn
+++ b/spec/reference.bqn
@@ -359,11 +359,18 @@ Join←{
 
 Group←{
   ! IsArray 𝕩
-  Chk←{!1==𝕩⋄!∧´Int¨𝕩⋄!∧´¯1≤𝕩⋄≠𝕩}
-  l←(1<≡)◶Chk‿{!1==𝕩⋄Chk¨𝕩}𝕨
-  ! l≤○≠≢𝕩
-  ! ∧´l=l≠⊸↑≢𝕩
-  (𝕨⊸=/𝕩˜)¨↕1+¯1⌈´⚇1𝕨
+  𝕨↩Pair∘ToArray⍟(2>≡)𝕨
+  ! 1==𝕨
+  {!∧´Int¨𝕩⋄!∧´¯1≤𝕩}∘⥊¨𝕨
+  n←+´=¨𝕨
+  ! n≤=𝕩
+  ! (∾≢⌜𝕨)≡n↑≢𝕩
+  𝕨↩⥊¨𝕨 ⋄ 𝕩↩((≠¨𝕨)∾n↓≢𝕩)⥊𝕩
+  (𝕨⊸=/𝕩˜)¨↕1+¯1⌈´¨𝕨
+}
+GroupInds←{
+  ! 1==𝕩
+  𝕩 ⊔ ↕ (1<≡)◶≠‿(∾≢¨) 𝕩
 }
 
 # Searching
-- 
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