Date: Fri, 4 May 2001 19:31:21 -0400 (EDT) From: Jan-Willem Maessen Alan Bawden writes:

A macro facility is like a pair of vise-grips (if you don't know what those are, see http://www.technogulf.com/ht-vise.htm).

I found myself laughing heartily at this apt analogy. I have heard vice grips described as "the wrong tool for every job." (My own experience with vice grips backs this up). I considered including that well-known quip in the paragraph where I tried to make it clear that I was -not- saying the same thing about macros. (While looking for a good online picture of vise-grips I came across a number of vise-grip horror stories -- the best was the guy who replaced the steering wheel in his car with a pair of vise-grips! But I digress...) So just to reiterate: the property of vise-grips I find analogous to a macro facility is that the more -other- tools you have available, the less often you need -this- one, nevertheless you still want this tool in your tool-box. That being said, there are a number of things one might want out of a macro facility, and I think they should be carefully distinguished: 1) The ability to name expressions without evaluating them, e.g. to cook up a facsimile of laziness. 2) The ability to parrot source code (and maybe source position) back at the user, e.g. Alan's assert macro, or its C equivalent. 3) The ability to create new binding constructs. 4) The ability to create new declaration constructs. I like this list. I'd love to see nice elegant programming language features for doing all of these things. Not only would I have to write fewer macros, but I'd probably be able to do many amazing -new- things. (Lazyness, for example, doesn't just eliminate the need for a lot of macros, it allows many new things that are beyond the reach of mere macrology!) I suspect, however, that even with everything on this list checked off, I'd still want macros. Because I doubt that this list is exhaustive. The example I pulled out of my hat led you to put item #2 on this list, but I wonder if you would have thought of #2 if you didn't have my example before you? If I had picked another example, I suspect this list would have looked different. - Alan