On Fri, 11 Sep 2009 18:32:44 -0500, Abdulaziz Ghuloum <[email protected]> wrote:
> Your technique for searching the input syntax for some identifier > is applicable even using syntax-rules only, so, I don't see how > outlawing syntax->datum is more necessary to ensure that we can't > "bind identifiers unhygienically" than outlawing syntax-rules. > > Google unhygienic syntax-rules for details. I retracted the use of the word "unhygienic" to apply to what that macro does: but I'm convinced that the macro I wrote there is not expressible using pure `syntax-rules'. Basically, if you have a top-level hook hiding around your macro call, you can do almost anything (which is the root of Oleg's technique), but you still are only able to compare identifiers using `free-identifier=?' - it's just that the scope you can do this in is the entire top-level form. The comparison of identifiers using `eq?' on the symbols is something that it's not possible to do without some variation of Oleg's technique of redefining binding constructs. -- Brian Mastenbrook [email protected] http://brian.mastenbrook.net/ _______________________________________________ r6rs-discuss mailing list [email protected] http://lists.r6rs.org/cgi-bin/mailman/listinfo/r6rs-discuss
