Implemented instruction splitting as a generator

src/token/Instructions.go

@@ -0,0 +1,61 @@
+package token
+
+// Instructions yields on each AST node.
+func (list List) Instructions(yield func(List) bool) {
+	start := 0
+	groupLevel := 0
+	blockLevel := 0
+
+	for i, t := range list {
+		switch t.Kind {
+		case NewLine:
+			if start == i {
+				start = i + 1
+				continue
+			}
+
+			if groupLevel > 0 || blockLevel > 0 {
+				continue
+			}
+
+			if !yield(list[start:i]) {
+				return
+			}
+
+			start = i + 1
+
+		case GroupStart:
+			groupLevel++
+
+		case GroupEnd:
+			groupLevel--
+
+		case BlockStart:
+			blockLevel++
+
+		case BlockEnd:
+			blockLevel--
+
+			if groupLevel > 0 || blockLevel > 0 {
+				continue
+			}
+
+			if !yield(list[start : i+1]) {
+				return
+			}
+
+			start = i + 1
+
+		case EOF:
+			if start < i {
+				yield(list[start:i])
+			}
+
+			return
+		}
+	}
+
+	if start < len(list) {
+		yield(list[start:])
+	}
+}