Instead of
(let [predicate #(contains? (set unselect) %1)] ...)
I would write
(let [predicate (set unselect)] ...)
On Tuesday, September 4, 2012 11:10:04 AM UTC+2, Marcus Lindner wrote:
>
> I wanted to use it to select a random element in a collection (set,
> vector or list) where I can define elements which should not be selected.
> The function I now use is:
>
> (defn select-random [collection & unselect]
> "(select-random collection & unselect) selects a random element from
> the specified 'collection'.
> It will ignore any element which is specified in 'unselect'. If none
> elements are specified in 'unselect',
> then any element from the specified 'collection' may be chosen. "
> ( let [predicate #(contains? (set unselect) %1)]
> (rand-nth (remove predicate collection))))
>
> Eventually this can be optimized for better reading and/or performance.
> It might be also a good idea to add some preconditions to it like
> {pre: [(coll? collection)] }.
>
> Am 03.09.2012 13:29, schrieb Tassilo Horn:
> > Goldritter <[email protected] <javascript:>> writes:
> >
> >> Ah ok. So I need to transform a vector and/or a list into a set first.
> > No, not really. All clojure collections implement java.util.Collection,
> > so you can always use
> >
> > (.contains your-coll something)
> >
> > to check if your-coll contains something. However, keep in mind that
> > this does a linear search for lists, sequences or vectors. So if your
> > algorithm relies on containment checks, you might be better off using
> > sets directly.
> >
> > Bye,
> > Tassilo
> >
>
>
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