On Oct 22, 2008, at 12:43 AM, Krukow wrote:
> Ok, thanks. I'm still a bit unsure as to how to think about it
> conceptually. I made the following experiment in the REPL
>
> user> (eval (list (symbol "Object.")))
> [EMAIL PROTECTED]
> user>
>
> This seems to indicate that actually Object. is just a symbol like any
> other. So there isn't any special reader support for it, but instead
> the compiler handles symbols with dots specially (depending on where
> the dot is in the symbol - beginning middle end).
Good experiment. Conceptually there is a time when macro forms are
expanded until there are no macros left in them. That's the time when
(X. ...) becomes (new X ...).
It appears that the expansion is done (in part) by the function
Compiler/macroexpand1. It's given a list to expand and it first checks
if the first item is a special form. If yes, there's no more expansion
to do. It then checks if it names a macro. If yes, it calls the macro
function to get the expansion. If not, it then checks if it's a symbol
with a leading period and expands appropriately if it is. Finally
(line 4041 of Compiler.java currently), it checks for a trailing
period. If yes, it replaces the expression with the equivalent "new".
You can see this in the REPL as:
user> (macroexpand-1 '(Object.))
(new Object)
There is also reader support for the trailing period (LispReader.java:
892), but that appears only to be used in the new "#=" reader macro.
--Steve
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