All of those create a copy of the array and do not modify the original, which may be important on cases like audio manipulation, where there are for instance 44,000 array entries per second. Furthermore, I wonder if D could automatically vectorize this operation when SSE/MMX style instructions are available?
It's not D that auto-vectorize such expression, it's the backend. Those "array ops" makes it easier for the compiler to convey that to the backend, though. Using LDC + arrays ops is often the best thing you can do speed-wise.
