Better yet,
(defmacro iff [test & {:keys [then else]}]
`(if ~test ~then ~else))
(that's doing the lookup for then and else in the map constructing
from the macro's rest argument at compilation time rather than in an
evaluated map including both at run time).
Cheers,
Michał
On 9 December 2012 00:40, Ben Wolfson <wolf...@gmail.com> wrote:
> You may want to use some delays to prevent evaluation of untaken branches:
>
> user=> (iff true :else (println 1) :then (println 3))
> 3
> 1
> nil
> user=>
>
>
> On Sat, Dec 8, 2012 at 3:02 PM, Thomas Goossens
> <cont...@thomasgoossens.be> wrote:
>> One of the issues i had and still have with the if function is that
>> because it has ordered arguments, makes things more complex.
>>
>> For small functions this is no so much of a problem.
>> (if test 1 0)
>>
>> But when things get larger, that extra complexity of order without explicit
>> information can get significant, I believe
>>
>> So I wanted (this would be officially my first macro ever!) something that
>> behaved as follows:
>>
>> (if test
>> :then true
>> :else false)
>>
>> (if test
>> :else false
>> :then true)
>>
>> Which is what I eventually did:
>>
>> (defmacro iff
>> [test & body]
>> (let [args (apply hash-map body)]
>> `(if ~test (:then ~args) (:else ~args))))
>>
>> Any thoughts, improvements on my macro? (Also I'm not quite sure how to
>> document my macro. So any advice on that is appreciated :)
>>
>>
>>
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>
>
>
> --
> Ben Wolfson
> "Human kind has used its intelligence to vary the flavour of drinks,
> which may be sweet, aromatic, fermented or spirit-based. ... Family
> and social life also offer numerous other occasions to consume drinks
> for pleasure." [Larousse, "Drink" entry]
>
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