If I could hazard a guess, it has to do with symbol lookup in maps.
Try the following:
('foo {'foo 1})
('foo {'bloo 1} 4)
when you do ('foo 1), it can't find foo in 1 (because it isn't there,
and 1 isn't even a map), so it returns nil. If you do ('foo 1 2),
you've just provided a default value, which it dutifully returns.
It's interesting that symbols don't care whether they are passed maps
or not----fun fact!
On Jan 3, 2:47 pm, Bill Caputo <logos...@gmail.com> wrote:
> Hi All,
>
> So, I've been doing some experimentation in order to better understand
> the reader, and I can't figure out why I get the following results for
> these four calls:
>
> => ('foo) ; ((quote foo))
> java.lang.IllegalArgumentException: Wrong number of args (0) passed
> to: Symbol (NO_SOURCE_FILE:0)
>
> => ('foo 1) ; ((quote foo) 1)
> nil
>
> => ('foo 1 2) ; ((quote foo) 1 2)
> 2
>
> => ('foo 1 2 3)
> java.lang.IllegalArgumentException: Wrong number of args (3) passed
> to: Symbol (NO_SOURCE_FILE:0)
>
> What I expected is that either foo would be invoked (and so I'd see an
> error because it didn't exist) *or* I'd get a list ala (foo 1 2)
> - further, I can't understand why I get "nil" for an arity of 1 but
> "2" for an arity of two).
>
> Anyone have an explanation? I'm off to find the impl for "Symbol" and
> see if I can figure out how it is being invoked here...
>
> Thanks,
> Bill
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