Note Colin, if I had declared foo differenlty, e.g. (defn foo [a b {:keys
[c d]}), that would be slightly different since it requires a map as third
argument. But that is not the case with
(defn foo [a b & {:keys [c d]}]). It may be using maps under the hood, but
none of my formal parameters are necessarily intended to be bound to maps
in this case, and I'm looking for a very fixed set of keywords in the
function call.
On Sun, Aug 23, 2015 at 10:17 AM, Dave Tenny <dave.te...@gmail.com> wrote:
> The point of my colorful title and judgmental post is that in the example,
> passing :e for the declared parameters as declared is a pointless operation
> at best, and in most practical situations it is also an erroneous
> operation.
>
> The language designers have (arguably for the good) chosen to complain
> about various actual argument mismatches vs. formal parameters.
>
> If I tried to call foo with only one argument I'd get an error about
> missing arguments (or more generally, arity).
> Similarly, in this case, calling foo with :e should complain about
> superfluous arguments, all assuming that foo is declared as intended.
> Without an :as option on the destructuring, there is nothing that can be
> done to meaningfully process a keyword to the function named :e.
>
> I am proposing the language should do better in this case. If not now,
> perhaps 2.0.
>
>
> On Sat, Aug 22, 2015 at 9:06 PM, Colin Yates <colin.ya...@gmail.com>
> wrote:
>
>> Hi Dave, it _isn't_ an Illegal argument though :-), your destructuring
>> is simply ignoring that parameter.
>>
>> However, I get the pain and solutions might be (in order of 'heavyness'):
>> - http://blog.fogus.me/2009/12/21/clojures-pre-and-post/
>> - https://github.com/Prismatic/schema
>> - http://typedclojure.org/
>>
>> HTH
>>
>> Dave Tenny writes:
>>
>> > I sure wish Clojure would generate "IllegalArgumentException" in the
>> > following sample case:
>> >
>> > (defn foo [a b & {:keys [c d]}] 1)
>> > (foo 1 2 :e 5) ; blithely ignores :e 5
>> >
>> > I understand that Clojure's destructuring things are very nice, and more
>> > powerful than Common Lisp's, and I like
>> > that when I need it.
>> >
>> > However I can't tell you how many times I've been bitten by this. Some
>> > simple typo or other other parameter name error on keyword arguments
>> > with untended and way-too-long-to-debug consequences.
>> >
>> > In my mind, on this subject, Common Lisp lambda lists got this right and
>> > Clojure gets a poor grade.
>> > Something about being doomed to repeat history. In Common Lisp, if you
>> > really wanted to allow other (arbitrary) keywords you'd
>> > just use &allow-other-keys.
>> >
>> > Maybe clojure should only allow the above case to go
>> un-complained-about if
>> > :as was specified for the map.
>> >
>> > If there's some automatic enforcement I'm missing that comes with 'defn'
>> > please let me know, I'm still learning the language.
>> >
>> > I've thought more that once about making a common lisp DEFUN statement
>> that
>> > maps to DEFN but implements
>> > lambda list semantics (including 'supplied-p' parameters). I've just
>> been
>> > too lazy to do it.
>> >
>> > It would also likely perform poorly after injecting the additional
>> > checks/rearrangements into the function on top of what Clojure has
>> already
>> > done,
>> > so I suppose it would have to be taken a step further so that it didn't
>> > generate DEFN expressions at all but was implemented at DEFN's level as
>> > a seperately named form.
>> >
>> > Tips welcome. Just thinking aloud.
>> >
>> > - Dave
>>
>> --
>> Sent with my mu4e
>>
>> --
>> You received this message because you are subscribed to the Google
>> Groups "Clojure" group.
>> To post to this group, send email to clojure@googlegroups.com
>> Note that posts from new members are moderated - please be patient with
>> your first post.
>> To unsubscribe from this group, send email to
>> clojure+unsubscr...@googlegroups.com
>> For more options, visit this group at
>> http://groups.google.com/group/clojure?hl=en
>> ---
>> You received this message because you are subscribed to a topic in the
>> Google Groups "Clojure" group.
>> To unsubscribe from this topic, visit
>> https://groups.google.com/d/topic/clojure/3-CevvzQg1s/unsubscribe.
>> To unsubscribe from this group and all its topics, send an email to
>> clojure+unsubscr...@googlegroups.com.
>> For more options, visit https://groups.google.com/d/optout.
>>
>
>
--
You received this message because you are subscribed to the Google
Groups "Clojure" group.
To post to this group, send email to clojure@googlegroups.com
Note that posts from new members are moderated - please be patient with your
first post.
To unsubscribe from this group, send email to
clojure+unsubscr...@googlegroups.com
For more options, visit this group at
http://groups.google.com/group/clojure?hl=en
---
You received this message because you are subscribed to the Google Groups
"Clojure" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to clojure+unsubscr...@googlegroups.com.
For more options, visit https://groups.google.com/d/optout.
