Implement pick ⊃

2 files changed, 32 insertions, 1 deletions

diff --git a/apl9.h b/apl9.h
index 83cee4a..0bfa6e9 100644
--- a/apl9.h
+++ b/apl9.h
@@ -344,6 +344,7 @@ Array *fnAnd(Array *, Array *);
 Array *fnNand(Array *, Array *);
 Array *fnNor(Array *, Array *);
 Array *fnTake(Array *, Array *);
+Array *fnPick(Array *, Array *);
 Array *fnIndex(Array *, Array *);
 Array *fnIndexOf(Array *, Array *);
 Array *fnMembership(Array *, Array *);
diff --git a/functions.c b/functions.c
index b72c2bd..1645e77 100644
--- a/functions.c
+++ b/functions.c
@@ -95,7 +95,7 @@ fndyad dyadfunctiondefs[] = {
 	fnTake, /* ↑ */
 	0, /* ↓ */
 	0, /* ⊂ */
-	0, /* ⊃ */
+	fnPick, /* ⊃ */
 	0, /* ⊆ */
 	fnIndex, /* ⌷ */
 	0, /* ⍋ */
@@ -1152,6 +1152,36 @@ fnTake(Array *left, Array *right)
 }
 
 Array *
+fnPick(Array *left, Array *right)
+{
+	if(left->rank > 1)
+		throwerror(nil, ERank);
+	if(left->size == 0)
+		return fnSame(right);
+
+	int io = globalIO();
+	Array *result = fnSame(right);
+	for(int i = 0; i < left->size; i++){
+		Array *ix = arrayitem(left, i);
+		if(ix->rank > 1)
+			throwerror(nil, ERank);
+		if(ix->size != result->rank)
+			throwerror(nil, ERank);
+		int index = 0;
+		for(int j = 0; j < ix->size; j++){
+			int add = ix->intdata[j] - io;
+			for(int k = j+1; k < ix->size; k++)
+				add *= result->shape[k];
+			index += add;
+		}
+		Array *tmp = result;
+		result = arrayitem(result, index);
+		freearray(tmp);
+	}
+	return result;
+}
+
+Array *
 fnIndex(Array *left, Array *right)
 {
 	int io = globalIO();