From cf4d42fc8ea7875a7df2e85688d1466ebbbbc36b Mon Sep 17 00:00:00 2001
From: Marshall Lochbaum <mwlochbaum@gmail.com>
Date: Mon, 28 Mar 2022 17:07:31 -0400
Subject: =?UTF-8?q?Support=20for=20=E2=88=BE=20and=20>=20in=20Under?=
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---
 src/r1.bqn | 25 +++++++++++++++++++------
 1 file changed, 19 insertions(+), 6 deletions(-)

(limited to 'src/r1.bqn')

diff --git a/src/r1.bqn b/src/r1.bqn
index f694b2fc..e34d28ba 100644
--- a/src/r1.bqn
+++ b/src/r1.bqn
@@ -377,12 +377,17 @@ under←{
 
   Expand ← {
     f‿a‿i‿q←𝕩 ⋄ e←i⊑⥊a
-    ⟨IsArray◶⟨⟨⟩,∾⟜⟨i⟩⟩f,e,IsArray◶⟨0,@Fill⥊⟜(↕1×´⊢)∘≢⟩e,q⟩
+    Expand2⍟(2=𝕨) ⟨IsArray◶⟨⟨⟩,∾⟜⟨i⟩⟩f,e,IsArray◶⟨0,@Fill⥊⟜(↕1×´⊢)∘≢⟩e,q⟩
+  }⍟(>⟜(IsArray 2⊑⊢))
+  Expand2 ← {
+    xf‿xa‿xi‿xq ← 𝕩
+    i ← { f‿a‿i‿q←1 Expand xf‿xa‿𝕩‿xq ⋄ {f‿a‿𝕩‿q _s}⍟(1-IsStruct)⌜i }⌜ xi
+    ⟨⟩‿@‿i‿⟨1,1⟩
   }
   _s ← {
     ⟨st,d‿o⟩←𝕩  # Function, input depth, output is structural
-    f‿a‿i‿⟨q,r⟩←Expand⍟(d>·IsArray 2⊑⊢)𝕗   # Path, array reference, indices, info
-    {f‿a‿𝕩‿⟨q⌈1<o,r⟩ _s}⍟(0<o) 𝕨 St i
+    f‿a‿i‿⟨q,r⟩←d Expand 𝕗   # Path, array reference, indices, info
+    {f‿a‿𝕩‿⟨q⌈1<o,r⟩ _s}⍟(1-IsStruct)⍟(0<o) 𝕨 St i
   }
   IsStruct ← (StructD←(4=0⊸⊑)◶⟨0,s˙=2⊸⊑⟩) {Decompose𝕩}
   NS ← IsStruct _errIf
@@ -392,6 +397,15 @@ under←{
     a ← Decompose⊸(1⊸⊑⊸((0<·≠0⊑⊣)◶⟨SD 2⊑⊣,{r↩1⋄𝕩}⟩) ⍟(StructD⊣)) _perv 𝕩
     ⟨⟩‿@‿a‿⟨d,r⟩ _s
   }
+  _nested ← {
+    p0‿p1←(⌊⋈⌈)´pw‿px←0⊸⊑⌜a←(1 Expand 1⊑Decompose)⌜ 𝕨‿𝕩
+    p ← 0+´×`(⊑⟜pw=⊑⟜px)⌜↕p0
+    (p↓0⊑a)
+    (p=p1)◶⟨
+      Nest 𝔽○{f‿a‿i‿q←𝕩⋄{f‿a‿𝕩‿q _s}⌜i}
+      {𝕩_s}(2↑⊢)∾𝔽○(2⊸⊑)⋈⌈¨○(3⊑⊢)
+    ⟩´a
+  }
 
   _amb ← {(IsStruct⊢)◶⟨𝕏, 𝕩‿𝕗{𝕨𝕏𝕗}⟩}
   _mon ← {(𝕗_amb𝕩)⊘(NS𝕩)}
@@ -408,8 +422,8 @@ under←{
     "⥊⌽⍉⊏",       1‿1 _amb
     "↑↓",         {(1‿2 _amb𝕩)⊘(1‿1 _amb𝕩)}
     "⊑",          1‿2 _amb
-  # ">",          2‿1 _mon
-  # "∾",          2‿1 _mon  # Dyad combines
+    ">",          2‿1 _mon
+    "∾",          2‿1 {+○IsStruct◶⟨𝕏, 𝕩‿𝕗{𝕨𝕏𝕗}⊘E, 𝕏_nested⟩}
   # "˘⎉¨⌜",
   # "⚇",
   ⟩
@@ -472,7 +486,6 @@ under←{
 
   _indRec ← {
     root‿x←𝕗 ⋄ iv←𝕩
-    "TODO"!0=≠root
     l ← GroupLen i ← (1=Type)◶⟨0⊑0⊑1⊑Decompose,¯1⟩⌜ 0⊑iv
     ind‿val ← (l GroupOrd i)⊸⊏⌜ iv ⋄ rec←0
     ic ← (1<·≠0⊑⊢)◶⟨2⊑⊢,{rec↩1⋄𝕩_s}(⋈1↓0⊑⊢)∾1↓⊢⟩∘(1⊑Decompose)⌜ ind
-- 
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