"Macro" considered harmful (01 May 2007)

In the OneSpace Modeling FAQ pages, I sometimes used or still use the term "macro" for the code snippets which I present there. Not a wise choice, as it occurred to me a while ago, and I intend to fix that now, or at least over time as I revisit those pages for other updates.

I used "macro" mostly for historical reasons. "Macro" is an overloaded term which can mean (too) many things:

  • In Lisp, a macro is a piece of code defined by defmacro. Macros in Lisp are a clever way to extend the language. If you want to learn more about this (or about Common Lisp in general, in fact), I recommend Peter Seibel's "Practical Common Lisp" - here's the section on macros.
  • CoCreate's 2D package, OneSpace Drafting, has a built-in macro interpreter which can be used to customize and extend the product. Since many OneSpace Drafting migrate from 2D to 3D, i.e. to OneSpace Modeling, they tend to take their nomenclature with them, and so they often call pieces of Lisp customization code a "macro", too.
  • In many software packages, users can record the interaction with the product and save the result into files, which are then often called macro files. OneSpace Modeling's recorder is such a mechanism, and so using the word "macro" is kind of natural for many users.

And so many users of OneSpace Modeling call their Lisp functions and customizations "macros", although this isn't really the correct term. Well, at least in most cases. Many of those customizations use an API called sd-defdialog which is provided by the "Integration Kit" library which ships with OneSpace Modeling. This API is, in fact, implemented using defmacro, i.e. sd-defdialog is itself a Lisp macro. So if a user writes code which builds on sd-defdialog and then calls the result a macro, he's actually not that far from the truth - although, of course, still incorrect.

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-- ClausBrod - 01 May 2007

Revision: r1.3 - 16 Jun 2007 - 13:49 - ClausBrod
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