Refactor Strip (already).

Stripping cards from the Hand will also be useful, so I pulled the logic of Strip out into arrayutil (more efficiently, too) and rewrote deck.Strip to use it.

cardsim/sliceutil.go

@@ -126,3 +126,22 @@ func ShufflePart[T any](slice []T, r *rand.Rand, loc, n int) {
 	}
 	ShuffleAll(slice[loc:loc+n], r)
 }
+
+// Strip iterates T, removing any element for which removeWhen returns true
+// (when provided the index of the element and the element itself as arguments).
+// It returns the stripped slice.
+func Strip[T any](slice []T, removeWhen func(idx int, t T) bool) []T {
+	if len(slice) == 0 {
+		return nil
+	}
+	to := 0
+	for from, e := range slice {
+		if !removeWhen(from, e) {
+			if to != from {
+				slice[to] = slice[from]
+			}
+			to++
+		}
+	}
+	return slice[:to]
+}