I really like the zap idea... although your second edit has a good point. But on the other hand, it wouldn't necessarily be a bad thing to allow macros in ssyntax, would it? Just a little difficult to implement perhaps. Or we could just get first class macros...
Another thing I've been thinking about would be allowing macros in call* type tables, e.g. allowing (3 + 4 * 5) to macro-expand instead of forcing infix math to be implemented as a function at runtime. (This would seamlessly integrate infix math into the regular syntax of Arc, with no performance penalty at all... something I personally would like to see.) But this would probably require type inference in the language, so might not be implementable in the near future.
