Implement windowed reduce

1 files changed, 15 insertions, 5 deletions

diff --git a/hybrids.c b/hybrids.c
index 8042e5d..e7f7f4b 100644
--- a/hybrids.c
+++ b/hybrids.c
@@ -166,9 +166,6 @@ fnExpandFirst(Array *left, Array *right)
 Array *
 opReduceLast(Datum *lefto, Array *left, Array *right)
 {
-	if(left)
-		throwerror(L"left argument to f/", ENotImplemented);
-
 	right = fnTranspose(right);
 	Array *tmp = opReduceFirst(lefto, left, right);
 	Array *res = fnTranspose(tmp);
@@ -194,8 +191,21 @@ opScanLast(Datum *lefto, Array *left, Array *right)
 Array *
 opReduceFirst(Datum *lefto, Array *left, Array *right)
 {
-	if(left)
-		throwerror(L"left argument to f⌿", ENotImplemented);
+	if(left){
+		if(left->type != AtypeInt)
+			throwerror(nil, EType);
+		if(left->size != 1)
+			throwerror(nil, ELength);
+		vlong winsize = left->intdata[0];
+		if(winsize > right->shape[0])
+			throwerror(nil, EShape);
+
+		Rune *code = L"n←(-|⍺)+1+≢⍵ ⋄"
+				L"ix←(⍳|⍺)∘+¨(⍳n)-⎕io ⋄"
+				L"ix←⍺{⍺<0:⌽¨⍵ ⋄ ⍵}ix ⋄"
+				L"↑⍵∘(⍶{⍶⌿(⊂⍵)⌷⍺})¨ix";
+		return rundfn(code, lefto, nil, left, right);
+	}
 
 	if(right->rank == 0)
 		return fnSame(right);