In PL/I evaluation is always broken off. The standard requires it. One must break up a single expression into several, using temporaries and some low cunning, to avoid break off.
Side effects can be beneficent or malign. Reflexive hostility to them, common among academic computer scientists, is drole where it is not worse. The real issue is one of performance, and for this reason all of the RDBMs that I am familiar with in detail in detail 1) do break off and 2) reorder predicates to increase its efficiency. It is perhaps worth noting that optimal ordering can be location- or -data-dependent. In the United States one would almost always wish to put the conjunctive predicate Speaks punjabi? before the predicate Is female? Punjabi speakers are uncommon here. In some parts of India and Pakistan the reverse, Is female? preceding Speaks punjabi? would be much better. Nearly everyone speaks punjabi, but only about half of the population is female. John Gilmore, Ashland, MA 01721 - USA ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
