On Sun, Feb 15, 2009 at 10:50 PM, David Nolen <dnolen.li...@gmail.com> wrote:
> Would it be possible to make the arguments to handle be optional? Is this a
> good or bad idea?
(kit/with-handler
(vec (map int-half [2 4 5 8]))
(kit/handle *odd-number-error* [n]
(throw (Exception. (format "Odd number %d in vector." n)))))
The args vector ([n] above) is actually a vector in a :keys
destructuring expression, so its elements are option. In fact map
being destructured has several other bit of information that may be
useful. You can see them like this:
(kit/with-handler
(vec (map int-half [2 4 5 8]))
(kit/handle *odd-number-error* {:as err}
err))
-> {:n 5, :tag user/*odd-number-error*,
:msg "Can't handle odd number: 5", :unhandled #<...>}
That map includes values inherited from parent error types. So you
can definitely leave the args vector empty.
I think it might be more confusing that useful to allow leaving out
the args vector entirely. Currently the expressions after the args
vector are expanded into an implicit 'do', so you can have as many as
you'd like. Detecting whether the first expression after the error
name is a vector (or map) and so should be treated as args vs. a list
to be an evaluated expression seems potentially confusing.
--Chouser
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