4 ms·

"Lisp has all the visual appeal of oatmeal with fingernail clippings mixed in." - Larry Wall C's macro system, for example, is so unreliable that you can't eve

"Lisp has all the visual appeal of oatmeal with fingernail clippings mixed in." - Larry Wall C's macro system, for example, is so unreliable that you can't even define a simple macro like #define square(x) x*x How do you set the value associated with the "foo" property? Oh, you use "setf", which rewrites (setf (get x foo) 1) to (LET* ((#:G847 X) (#:G848 FOO)) (MULTIPLE-VALUE-BIND (#:G850) 1 (COMMON-LISP::%PUT #:G847 #:G848 #:G850))) but you don't have to know that. It just works. I agree about C macros. But, show me the source for: (defmacro setf ... and you may be quoting Larry Wall.

almost 14y ago
I know you didn't actually mean it but here's an implementation of setf from GNU Emacs: https://gist.github.com/3116185#L1950 https://gist.github.com/3116185#L1950 It's actually not hard to understand if you know a bit of elisp. And of course the implementation of Macros is usually the hairiest bits of Lisp code. The thing about Macros is that you don't often want to write them, but when you do they allow you to do amazing things that simply wouldn't be possible without them.
drostie 14y ago
Since it's only 30 lines of code, here's the relevant section from SBCL (as found in src/code/early-setf.lisp): (defmacro-mundanely setf (&rest args &environment env) #!+sb-doc "Takes pairs of arguments like SETQ. The first is a place and the second is the value that is supposed to go into that place. Returns the last value. The place argument may be any of the access forms for which SETF knows a corresponding setting form." (let ((nargs (length args))) (cond ((= nargs 2) (let ((place (first args)) (value-form (second args))) (if (atom place) `(setq ,place ,value-form) (multiple-value-bind (dummies vals newval setter getter) (sb!xc:get-setf-expansion place env) (declare (ignore getter)) (let ((inverse (info :setf :inverse (car place)))) (if (and inverse (eq inverse (car setter))) `(,inverse ,@(cdr place) ,value-form) `(let* (,@(mapcar #'list dummies vals)) (multiple-value-bind ,newval ,value-form ,setter)))))))) ((oddp nargs) (error "odd number of args to SETF")) (t (do ((a args (cddr a)) (reversed-setfs nil)) ((null a) `(progn ,@(nreverse reversed-setfs))) (push (list 'setf (car a) (cadr a)) reversed-setfs)))))) Okay, so it's not the simplest thing around, and it hinges upon a bunch of other things also defined in the source. Nonetheless it's not very "oatmeal and fingernail clippings" after all. It's pretty straightforward. "Here is my docstring, let `nargs` be the number of arguments, if this is 2, then we've either got the primitive case (setf a 1) which is actually a `setq`, or else we macro-expand the place which should be a list like `(car a)`, pull off that first symbol `(car place)`, get its function -- call that function `inverse`, then return an expression which will call `inverse` on the `(cdr place)` with the `value-form` we're trying to set to. If this inverse doesn't exist then there seems to be some transformation of the list (a comment would have been nice here, because I'm not sure what this describes). If the number of args is odd then that's an error; if it's an even number greater than two then we assume that the syntax was (setf a 1 b 2) and recurse on the child pairs." As readability goes, it's not bad.
JustinJ70s 14y ago
"Lisp has all the visual appeal of oatmeal with fingernail clippings mixed in." - Larry Wall Considering the general appearance of code for the language he created I'm not sure this quote of his can be taken all that seriously. At worst Perl looks like somebody glued the shift key down and repeatedly head-butted the top row of their keyboard.
- berntb 14y ago
  (I shouldn't comment on karma 18 accounts, I'm probably being trolled, but a couple of links should be ok...) See the Synopsises here: http://search.cpan.org/~flora/MooseX-Declare-0.35/lib/MooseX/Declare.pm http://search.cpan.org/~flora/MooseX-Declare-0.35/lib/MooseX... http://search.cpan.org/~ether/MooseX-Method-Signatures-0.43/lib/MooseX/Method/Signatures.pm http://search.cpan.org/~ether/MooseX-Method-Signatures-0.43/... (I assume you'll insist that any link I give is ugly. :-) But note that the declarations and parameter specifications are at least as elegant as any other major scripting language I'm aware of.) Edit: And for the record, I love Perl and Lisp. :-)
  - JustinJ70s 14y ago
    Not trolled, probably karma 18 because I've posted only a few times in the years since creating an account. I'm really not intrested in karma/scoring games on sites like HN. Moose looks really nice and I've nothing against Perl - my language of choice is Scala. I just thought it was a daft thing for Larry to say considering the issues of readability that have been levelled at Perl.
    - mst 14y ago
      If you consider this, what you've just said is "I think it's daft for Larry not to like the way lisp looks considering some people don't like the way perl looks." I don't like the way python looks. Does that mean it would be daft for Guido to ever criticise another language's aesthetics? :)

almost 14y ago

I know you didn't actually mean it but here's an implementation of setf from GNU Emacs: https://gist.github.com/3116185#L1950 https://gist.github.com/3116185#L1950 It's actually not hard to understand if you know a bit of elisp. And of course the implementation of Macros is usually the hairiest bits of Lisp code. The thing about Macros is that you don't often want to write them, but when you do they allow you to do amazing things that simply wouldn't be possible without them.

drostie 14y ago

Since it's only 30 lines of code, here's the relevant section from SBCL (as found in src/code/early-setf.lisp): (defmacro-mundanely setf (&rest args &environment env) #!+sb-doc "Takes pairs of arguments like SETQ. The first is a place and the second is the value that is supposed to go into that place. Returns the last value. The place argument may be any of the access forms for which SETF knows a corresponding setting form." (let ((nargs (length args))) (cond ((= nargs 2) (let ((place (first args)) (value-form (second args))) (if (atom place) `(setq ,place ,value-form) (multiple-value-bind (dummies vals newval setter getter) (sb!xc:get-setf-expansion place env) (declare (ignore getter)) (let ((inverse (info :setf :inverse (car place)))) (if (and inverse (eq inverse (car setter))) `(,inverse ,@(cdr place) ,value-form) `(let* (,@(mapcar #'list dummies vals)) (multiple-value-bind ,newval ,value-form ,setter)))))))) ((oddp nargs) (error "odd number of args to SETF")) (t (do ((a args (cddr a)) (reversed-setfs nil)) ((null a) `(progn ,@(nreverse reversed-setfs))) (push (list 'setf (car a) (cadr a)) reversed-setfs)))))) Okay, so it's not the simplest thing around, and it hinges upon a bunch of other things also defined in the source. Nonetheless it's not very "oatmeal and fingernail clippings" after all. It's pretty straightforward. "Here is my docstring, let `nargs` be the number of arguments, if this is 2, then we've either got the primitive case (setf a 1) which is actually a `setq`, or else we macro-expand the place which should be a list like `(car a)`, pull off that first symbol `(car place)`, get its function -- call that function `inverse`, then return an expression which will call `inverse` on the `(cdr place)` with the `value-form` we're trying to set to. If this inverse doesn't exist then there seems to be some transformation of the list (a comment would have been nice here, because I'm not sure what this describes). If the number of args is odd then that's an error; if it's an even number greater than two then we assume that the syntax was (setf a 1 b 2) and recurse on the child pairs." As readability goes, it's not bad.

JustinJ70s 14y ago

"Lisp has all the visual appeal of oatmeal with fingernail clippings mixed in." - Larry Wall Considering the general appearance of code for the language he created I'm not sure this quote of his can be taken all that seriously. At worst Perl looks like somebody glued the shift key down and repeatedly head-butted the top row of their keyboard.

berntb 14y ago
(I shouldn't comment on karma 18 accounts, I'm probably being trolled, but a couple of links should be ok...) See the Synopsises here: http://search.cpan.org/~flora/MooseX-Declare-0.35/lib/MooseX/Declare.pm http://search.cpan.org/~flora/MooseX-Declare-0.35/lib/MooseX... http://search.cpan.org/~ether/MooseX-Method-Signatures-0.43/lib/MooseX/Method/Signatures.pm http://search.cpan.org/~ether/MooseX-Method-Signatures-0.43/... (I assume you'll insist that any link I give is ugly. :-) But note that the declarations and parameter specifications are at least as elegant as any other major scripting language I'm aware of.) Edit: And for the record, I love Perl and Lisp. :-)
- JustinJ70s 14y ago
  Not trolled, probably karma 18 because I've posted only a few times in the years since creating an account. I'm really not intrested in karma/scoring games on sites like HN. Moose looks really nice and I've nothing against Perl - my language of choice is Scala. I just thought it was a daft thing for Larry to say considering the issues of readability that have been levelled at Perl.
  - mst 14y ago
    If you consider this, what you've just said is "I think it's daft for Larry not to like the way lisp looks considering some people don't like the way perl looks." I don't like the way python looks. Does that mean it would be daft for Guido to ever criticise another language's aesthetics? :)