From 22858219b44dcc483aecc40297cea28a02625972 Mon Sep 17 00:00:00 2001
From: Peter Mikkelsen <petermikkelsen10@gmail.com>
Date: Fri, 28 Jan 2022 15:40:40 +0000
Subject: =?UTF-8?q?Implement=20membership=20(X=E2=88=8AY),=20excluding=20(?=
 =?UTF-8?q?X~Y)=20and=20union=20(X=E2=88=AAY)?=
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---
 apl9.h      |  3 +++
 eval.c      |  2 +-
 functions.c | 27 ++++++++++++++++++++++++---
 3 files changed, 28 insertions(+), 4 deletions(-)

diff --git a/apl9.h b/apl9.h
index 311bceb..2846861 100644
--- a/apl9.h
+++ b/apl9.h
@@ -340,6 +340,9 @@ Array *fnNand(Array *, Array *);
 Array *fnNor(Array *, Array *);
 Array *fnTake(Array *, Array *);
 Array *fnIndex(Array *, Array *);
+Array *fnMembership(Array *, Array *);
+Array *fnUnion(Array *, Array *);
+Array *fnExcluding(Array *, Array *);
 Array *fnCatenateLast(Array *, Array *);
 Array *fnCatenateFirst(Array *, Array *);
 Array *fnReshape(Array *, Array *);
diff --git a/eval.c b/eval.c
index 8829609..5a8d758 100644
--- a/eval.c
+++ b/eval.c
@@ -31,7 +31,7 @@ int bindingstrengths[11][11] = {
 	6, 6, 6, 0, 0, 0, 0, 0, 0, 0, 0, /* DO */
 	3, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, /* AF */
 	0, 0, 0, 0, 0, 0, 0, 8, 9, 0, 0, /* ( */
-	0, 0, 0, 0, 0, 0, 0, 0, 9, 0, 0, /* ) */
+	8, 8, 8, 8, 8, 8, 8, 8, 9, 8, 8, /* ) */
 	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, /* ← */
 	1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, /* IS */
 	0, 0, 0, 0, 0, 0, 0, 0, 9, 0, 0, /* N */
diff --git a/functions.c b/functions.c
index eedacb9..ad87c11 100644
--- a/functions.c
+++ b/functions.c
@@ -102,11 +102,11 @@ fndyad dyadfunctiondefs[] = {
 	0, /* ⍒ */
 	0, /* ⍳ */
 	0, /* ⍸ */
-	0, /* ∊ */
+	fnMembership, /* ∊ */
 	0, /* ⍷ */
-	0, /* ∪ */
+	fnUnion, /* ∪ */
 	0, /* ∩ */
-	0, /* ~ */
+	fnExcluding, /* ~ */
 	fnCatenateLast, /* , */
 	fnCatenateFirst, /* ⍪ */
 	fnReshape, /* ⍴ */
@@ -1136,6 +1136,27 @@ fnIndex(Array *left, Array *right)
 	return result;
 }
 
+Array *
+fnMembership(Array *left, Array *right)
+{
+	/* TODO avoid outer product */
+	return rundfn(L"∨/⍺≡⌾⍵", nil, nil, left, right);
+}
+
+Array *
+fnUnion(Array *left, Array *right)
+{
+	if(left->rank > 1 || right->rank > 1)
+		throwerror(nil, ERank);
+	return rundfn(L"⍺⍪⍵~⍺", nil, nil, left, right);
+}
+
+Array *
+fnExcluding(Array *left, Array *right)
+{
+	return rundfn(L"(~⍺∊⍵)⌿⍺", nil, nil, left, right);
+}
+
 Array *
 fnCatenateLast(Array *left, Array *right)
 {
-- 
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