alf@sics.se (Thomas Sj|land) (10/19/88)
In <849@etive.ed.ac.uk> jha@lfcs.ed.ac.uk (Jamie Andrews) writes many things that I agree to fully. I would just like to clarify the point I made about intension since others have asked about it also. The only point I really wanted to make was to point out the vagueness of the notion of "declarative language", which is used more and more often these days. J.A. writes: >>My view: "(declarative programming <-> programming without added intension)" > > I'm not sure what you mean by "added intension". Do you mean >implementation considerations that make the program do more or less >than it would seem to from a purely declarative reading? No, what I mean by "added intension" is the possible lack of correspondence between the intension I have about the meaning of the program and the meaning as expressed by the "purely declarative reading" (Btw: Is there an "unpurely" declarative reading ?) of the program I write. In program transformation (manual or mechanical) this shows up in various situations. One of them is involved in exchange of representational terms in logic programs, like in the introduction of diff-structures. The ideal is that we should be able to use strictly logical considerations in the transformations, but it often turns out that operational invariants must be used to guide the transformation algorithm. So even if there is a nice completeness result for SLD-resolution we cannot use it for anything real, it seems, or am I too pessimistic ? -- Thomas Sj|land SICS, PO Box 1263, S-164 28 KISTA, SWEDEN Tel: +46 8 752 15 42 Ttx: 812 61 54 SICS S Fax: +46 8 751 72 30 Internet: alf@sics.se or {mcvax,munnari,ukc,unido}!enea!sics.se!alf