On Wed, May 25, 2011 at 9:40 PM, Marco Antoniotti antoniotti.marco@disco.unimib.it wrote:
Hi I don't think there is a reasonable objection to forbid a form like ((returns-something-funcallable arg1 arg2 ... argN) 1 2 3 ... N) from "working as expected".
Me neither ;)
As Martin pointed out, if the return value of the form is a "macro" then this would have to be interpreted in the "regular" evaluation regime. As per "extending" LET there have been a lot of proposals... IMHO a nice one is to go the LOOP way :) (LETS [var <symbol> <form>]* [fun (<name> <arglist> <body>)]* [labels (<name> <arglist> <body>)]* [values <list> <form>]* IN <body>) Of course you can add some ways of extending the syntax by having something like (def-lets-binding <tag> ...) You get the idea....
It's not about syntax, it's about a missing feature: the ability to bind a symbol's function "cell" to a value that's not known at compile time. To me, that's a limitation of the spec; given that we have funcall, it's obviously easy to implement and would be symmetrical to let. With such a feature, the gap between Lisp-1 and Lisp-2 would be effectively reduced:
(let ((list 42)) (flet ((list (compose #'nreverse #'list))) (list #'list list)))
=> (42 #<compiled-function (lambda (...) ...)>)
The code above is horrible, but you get the idea.
Alessio