when is like do with only the 'then' branch wrapped in a do:
(if foo
(do
(println "hi")
42)))
is the same as
(when foo
(println "hi")
42)
And like if without an else branch, when returns nil if its predicate
yields false.
On Jan 24, 9:33 am, wubbie <sunj...@gmail.com> wrote:
> Here is code from core.clj.
> The question is when to use when or if.
>
> (defn take
> "Returns a lazy seq of the first n items in coll, or all items if
> there are fewer than n."
> [n coll]
> (when (and (pos? n) (seq coll))
> (lazy-cons (first coll) (when (> n 1) (take (dec n) (rest
> coll))))))
>
> (defn drop
> "Returns a lazy seq of all but the first n items in coll."
> [n coll]
> (if (and (pos? n) (seq coll))
> (recur (dec n) (rest coll))
> (seq coll)))
>
> -sun
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