libera/#commonlisp - IRC Chatlog

4:32:32 beach Renfield: The macro call (USE-PARAM) is expanded at compile-time, and the expansion contains the value of *MY-PARAM* at compile time. The symbol *MY-PARAM* does not appear in the expansion, so it does not appear in the body of the LET.

4:35:25 beach Renfield: If you just do (MACROEXPAND-1 '(WINDOW::USE-PARAM)) you will see what it expands to.

4:38:20 MommyDearest ** NICK BrokenCog

4:50:30 beach Renfield: I am not sure what you are trying to do, but if you define USE-PARAM as (DEFMACRO USE-PARAM () '`(,*MY-PARAM*)) you will get *MY-PARAM* in the expansion, rather than its value.

4:51:23 beach ACTION is now convinced that the real use case is more complicated, and that his suggestions won't work in the real case.

12:03:53 younder (defun string-join (&rest strings &key (sep " ")) ...) as this (string-join "the" "fat" "cat" "shat" "on" "the" "mat") gives the error "odd number of &KEY arguments". Why?

12:05:54 beach Because every parameter is a &KEY parameter (and there is only one of them) so there must be an even number of arguments.

12:07:51 younder I read it a list of strings and a optional separator sep which defaults to " "

12:08:32 beach But that's not what it means.

12:08:41 younder Not optional - a keyword with a default argument

12:09:49 younder Well that makes no sense to me. Why does does it think the is a key?

12:09:58 younder "the"

12:10:47 beach Your definition means a function that takes only keyword arguments (so there must be an even number of arguments), and whatever arguments you pass are going to end up in the STRINGS &REST parameter.

12:10:48 _death clhs 3.4.1.4

12:10:49 specbot Specifiers for keyword parameters: http://www.lispworks.com/reference/HyperSpec/Body/03_dad.htm

12:11:09 _death "In this case the remaining arguments are used for both purposes; that is, all remaining arguments are made into a list for the rest parameter, and are also processed for the &key parameters."

12:12:41 _death in your case, either remove &rest specifier and just pass a list of strings and possible key arguments (the sane option), or leave &rest and remove &key and do your own keyword-like processing in the function (the stareyed teenage lisper option)

12:14:44 beach _death: How would removing the &REST parameter make it possible to pass a list of strings?

12:15:05 _death beach: the signature would then be (defun string-join (strings &key (sep ...)) ...)

12:15:21 beach Ah, so you mean add a required parameter, which you didn't say.

12:15:34 _death beach: right, I said remove the specifier not the variable

12:15:38 younder _death, yeah that's what I did

12:16:05 beach _death: That's a "lambda-list keyword", not a "specifier".

12:16:25 beach ... which is why I didn't understand.

12:17:11 _death beach: you're right :)

12:17:24 younder just (string-join (list "string1 "string2"))

12:25:07 _death beach: (just a small note, lambda-list keywords are specifiers.. I could've been more specific)

12:30:36 _death ok, I'm wrong again :).. "Each element of a lambda list is either a parameter specifier or a lambda list keyword.", so the specifier would be the symbol STRINGS.. now I need to internalize this terminological update ;)

12:46:05 dnhester` does anyone here use coleslaw?

12:52:03 beach _death: Good luck! :)

13:43:34 younder I think I finally got the rationale after reading https://www.cs.cmu.edu/Groups/AI/html/cltl/clm/node64.html

13:45:41 jcowan I'm done here, at least for the present. I'll still be available on #scheme (or so I expect) and #lisp (or so I expect).

13:47:05 younder The hyperspec is too obtuse for me, I need examples.

15:11:28 edgar-rft younder: Practical Common Lisp has a whole chapter about &optional, &rest, and &key parameters and what happens if you mix them with examples -> https://gigamonkeys.com/book/functions