While packed arrays may sound quite mysterious and deep, the idea is really quite simple. When it is clearly appropriate to represent a list of single-type machine numbers (integer, real, or complex) internally as an array, Mathematica does so. The basic technology is actually there in Mathematica 3.0, and is visible in the
List operations which were added to the compiler. Basically what we have done for Mathematica 4.0 is to extend this representation to kernel functions where it is appropriate. The internal representation is essentially invisible to you as a user (you have to use functions in the
Developer` context even to see it), so you do not have to worry about it. However, understanding the packed array representation can help you write faster more memory-efficient code. This article is intended to give you the information you need.
Converted by Mathematica
May 1, 2000