Re: a convenience idea for test functions
That is an excellent point, and the macro is actually a very nice approach, thanks for the help. On Apr 18, 1:07 am, Sean Corfield seancorfi...@gmail.com wrote: On Tue, Apr 17, 2012 at 9:16 PM, Dmitri dmitri.sotni...@gmail.com wrote: (map? foo bar baz) would return bar if foo is a map and baz otherwise. To elaborate on Alan's response, consider: (if (map? foo) (/ bar 0) baz) If map? were 'merely' a variadic function, (map? foo (/ bar 0) baz) would fail because (/ bar 0) would be evaluated and then passed as an argument, along with foo and baz. So, no, the simple answer is that you can't just make the test functions variadic and get the same behavior as an if form (hence Alan's suggestion of a macro-generating macro to create new macros for the forms you want). (Apologies if I'm laboring the point here) -- Sean A Corfield -- (904) 302-SEAN An Architect's View --http://corfield.org/ World Singles, LLC. --http://worldsingles.com/ Perfection is the enemy of the good. -- Gustave Flaubert, French realist novelist (1821-1880) -- 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
a convenience idea for test functions
Often times I find myself writing code like the following (if (map? foo) bar baz) would it make sense to make test functions variadic, so if only passed a single argument it would return true/false, but could also act as an if when passed 3 arguments, eg: (map? foo bar baz) would return bar if foo is a map and baz otherwise. -- 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
Re: a convenience idea for test functions
IMO this is fairly absurd for a language default, but you can easily
do this yourself in a number of ways. For example:
(defmacro define-preds [ preds]
(cons `do
(for [pred preds]
`(defmacro ~(symbol (str pred +)) ~'[obj then else]
(list '~'if (list '~pred ~'obj)
~'then ~'else)
(define-preds map? string?)
(map?+ {} 1 2) ;; 1
This would be quite a lot easier if we didn't care about the short-
circuiting behavior of 'if, since then a simple higher-order function
would do it, something like (defn as-switch [pred] (fn [obj then else]
(if (pred obj) then else))).
On Apr 17, 9:16 pm, Dmitri dmitri.sotni...@gmail.com wrote:
Often times I find myself writing code like the following
(if (map? foo) bar baz)
would it make sense to make test functions variadic, so if only passed
a single argument it would return true/false, but could also act as an
if when passed 3 arguments, eg:
(map? foo bar baz) would return bar if foo is a map and baz otherwise.
--
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Re: a convenience idea for test functions
On Tue, Apr 17, 2012 at 9:16 PM, Dmitri dmitri.sotni...@gmail.com wrote: (map? foo bar baz) would return bar if foo is a map and baz otherwise. To elaborate on Alan's response, consider: (if (map? foo) (/ bar 0) baz) If map? were 'merely' a variadic function, (map? foo (/ bar 0) baz) would fail because (/ bar 0) would be evaluated and then passed as an argument, along with foo and baz. So, no, the simple answer is that you can't just make the test functions variadic and get the same behavior as an if form (hence Alan's suggestion of a macro-generating macro to create new macros for the forms you want). (Apologies if I'm laboring the point here) -- Sean A Corfield -- (904) 302-SEAN An Architect's View -- http://corfield.org/ World Singles, LLC. -- http://worldsingles.com/ Perfection is the enemy of the good. -- Gustave Flaubert, French realist novelist (1821-1880) -- 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
