On 2 July 2010 15:50, Meikel Brandmeyer <m...@kotka.de> wrote:
> Then there are examples like this one:
> (reduce '* '(1 2 3))
>
> Someone who is new to Clojure and tries to understand reduce... Does
> he understand why the result is 3? A result which relies on a not very
> well-known fact, that you can actually call symbols like keywords for
> map lookup with up to two arguments. (I bet there quite a few of
> "seasoned" clojurians who didn't know that) I - if I was a newbie to
> the language - would mainly think: wtf?
Even with your explanation, I'm baffled... I can get to
user=> ('* ('* 1 2) 3)
3
Ah. This means look '* up in ('* 1 2) and use 3 as the default if you
don't find it. And you don't (for all sorts of odd reasons - why
doesn't this raise a "what are you doing, it's not even a map you're
looking up in" exception? :-)), so the result is the default, 3.
Uh, yeah.
That example is actually harmful - as it confused me about what does
and doesn't need quoting - something I would probably have got right
instinctively until I read this :-(
Paul.
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