On May 25, 2011, at 23:05 , Alessio Stalla wrote: > On Wed, May 25, 2011 at 9:40 PM, Marco Antoniotti > <antoniotti.ma...@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.
Yep. This has been discussed before (*)... If I remember correctly you can get almost there by specifying differently what you are doing when dealing with the OP of a form, when this is a symbol. My recollection is that it is doable and that the rationale for not allowing it is mostly to make compiler writing easier (although I think that that should be a piece of cake today). The problem is that you have to prioritize the namespace you are searching, thus ushering in a more complex set of rules for the programmer to remember. IMHO, this is not a very good reason to "leave it out" since it has been proved over and over again that languages which increase a programmer's self esteem are also those with the absolutely most convoluted access rules ever :) Plus these languages are also very successful :) Cheers -- Marco (*) It's in CLL. -- Marco Antoniotti, Associate Professor tel. +39 - 02 64 48 79 01 DISCo, Università Milano Bicocca U14 2043 http://bimib.disco.unimib.it Viale Sarca 336 I-20126 Milan (MI) ITALY Please note that I am not checking my Spam-box anymore. Please do not forward this email without asking me first. _______________________________________________ pro mailing list pro@common-lisp.net http://lists.common-lisp.net/cgi-bin/mailman/listinfo/pro
