Ruby/CArray adds multi-dimensional numerical arrays to Ruby. Elements are held in a single flat memory block, so whole-array work -- element-wise arithmetic, reductions along any axis, sorting, searching -- runs in C. Slicing, transposing, reshaping, and selecting by a boolean condition all return views that share storage with the original array and can be chained freely; nothing is copied until you ask for a copy. Any array, view included, can carry a mask marking individual elements as undefined, and arrays are exchanged with other numerical libraries without copying through Ruby's MemoryView protocol.