Path: utzoo!utgpu!watmath!att!cbnewsc!nevin1 From: nevin1@cbnewsc.ATT.COM (nevin.j.liber) Newsgroups: comp.lang.misc Subject: Re: What I'd really like to see in an if-statement... Message-ID: <2451@cbnewsc.ATT.COM> Date: 16 Aug 89 01:14:37 GMT References: <178@enea.se> Reply-To: nevin1@ihlpb.ATT.COM (nevin.j.liber) Organization: AT&T Bell Laboratories Lines: 37 In article <178@enea.se> sommar@enea.se (Erland Sommarskog) writes: >Actually I have always been surprised that no language I have dealt >have had this feature since it is so easy to implement. Am I overlook- >ing something? There are a few things. In evaluating the following expression: a < b < c < ... < n where a,b,c,...,n are arbituary EXPRESSIONS which *may have side effects* (something which mathematicians using this notation don't normally deal with), these are some of the issues which arise: Is the order of evaluation left to right, right to left, or arbituary? If "a < b" is false, is c necessarily still evaluated? Are a,b,c,...,n each evaluated only once, at most once, or as many times as necessary? The answers to these questions have a profound effect on the spirit of the language, the style of code written in the language, the implementation of the language, the possible optimisations for the language, etc. Different languages will have different answers to these questions (as well as the question "Does this construct really fit in with the rest of the language?"). Although at a first pass it is easy to implement, the real question becomes "Will this construct be truly beneficial to the language?" Or, rephrasing this question pessimistically, "Overall, will this construct be detrimental to the language?" -- _ __ NEVIN ":-)" LIBER nevin1@ihlpb.ATT.COM (312) 979-4751 IH 4F-410 ' ) ) "We are almost into the '90s; *nothing* is wierd." / / _ , __o ____ -- Buzz Kelman, Newsman & Bluesman, WLUP, 7/28/89 / (_