Simple Space Efficient Functions

Abstract

The demand driven evaluation technique described in the last chapter works best with functions that are space efficient. In general, space efficient functions are characterized by the fact that individual elements of the result can be computed independently of each other, and the actions involved in this computation depend only upon the indices of the elements being computed, not upon the value of those elements. Not all APL functions are space efficient; however, the majority (and more importantly, the most commonly used functions) do possess this property.