Higher-order Programming in an Or-intensive Style

Because implementations tend to favour a recursive deterministic AND-intensive programming style, it seems counter intuitive that a backtrack-ing findall-based paradigm can be more eecient. This is explained by a source level technique which is called goal precomputation, by a heap-based copy-once ndall and optimized meta predicates. A precomputed goal containing a future (reusable) computation is backtracked over instead of being constructed repeatedly. These techniques are enough, in terms of eeciency, to rehabilitate a generator based OR-intensive programming style. On the other side, we will try to nd out how to improve the traditional AND-intensive implementation of higher-order primitives and study the impact of meta-programming constructs like call/N. We introduce a newùniversal' higher-order predicate implemented also with goal precomputation which combines on the y selected answers from a generator. By using it for the executable speciication of key higher-order Prolog constructs, we point out the (unsuspected) expressive power of a pure OR-intensive programming style.