On Mon, 28 Jun 2010 13:31:45 -0500
Savanni D'Gerinel <sava...@alyra.org> wrote:
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> Along those lines, why is the apply necessary?
>
> More clearly, and I encountered this with a different block of code
> earlier today, repeat returns a lazy sequence. Str does nothing to
> evaluate that sequences, so (str (repeat ...)) returns a lazy sequence.
str applys .toString to it's arguments, and then concatenates the
results together. .toString of a lazy sequence is an internal token
that you can use to infer it's from a lazy sequence, and that's about
it.
> Why does (apply str (repeat ...)) evaluate the sequence? The
> documentation for apply does not mention that it will do so.
apply turns the values in sequence into arguments to a call to
str. For example, (apply str ["a" "b" "c"]) evaluates (str "a" "b" "c").
Since function arguments are passed by value (you can't apply a
macro), the lazy sequence has to be evaluated out to the end.
> Generally I am having a lot of trouble with sequences because I am never
> clear on when a lazy sequence will be evaluated strictly.
Sorry if this was already answered; I found it and realized I hadn't
seen an answer yet.
<mike
--
Mike Meyer <m...@mired.org> http://www.mired.org/consulting.html
Independent Network/Unix/Perforce consultant, email for more information.
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