Hmm, okay, so if "apply" unpacks all the arguments and feeds them all to my
anonymous function, then this should work:
(apply #([& everything] println first everything) @visitors)
but instead I get:
Unable to resolve symbol: & in this context
[Thrown class java.lang.RuntimeException]
Please note, I ask this only out of intellectual curiosity. In my code I'll
always use "map" in this circumstance. But I want to understand what apply
really does, and I'm clearly missing something.
On Tuesday, July 17, 2012 3:13:04 PM UTC-4, Mark Rathwell wrote:
>
> > your apply will end up doing sometihng like this:
> > (#(println %1) "stu" "mary" "lawrence")
> >
> > since apply takes @visitors as a collection and passes each item as an
> > argument to the function you give it.
>
> In other words, apply essentially unpacks the collection and passes
> the items as individual arguments to the specified function. str
> takes any number of arguments, so it works well with apply in your
> case. Your anonymous function is a one-argument function, but apply
> sends all items in your collection as arguments, and if your
> collection contains more than one element then that will be the wrong
> number of arguments.
>
> map is mapping the specified function to each element in the
> collection, one at a time, and returning a collection of the results.
> apply is calling the function once, but with all elements in the
> collection as the arguments and returning the result of that one
> function call.
>
> On Tue, Jul 17, 2012 at 2:35 PM, Jack Moffitt <j...@metajack.im> wrote:
> >
> > > So far, everything is working as I thought. But I also thought that
> apply
> > > let me run a function on everything in a sequence. Other than "str", I
> could
> > > not get this to work:
> > >
> > > user> (apply #(println %1) @visitors)
> >
> > I think you are looking for direct invocation:
> >
> > (#(println %1) @visitors)
> >
> > your apply will end up doing sometihng like this:
> > (#(println %1) "stu" "mary" "lawrence")
> >
> > since apply takes @visitors as a collection and passes each item as an
> > argument to the function you give it.
> >
> > jack.
> >
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