On Jan 25, 2:30 pm, Laurent PETIT <laurent.pe...@gmail.com> wrote:
> 2011/1/25 Shantanu Kumar <kumar.shant...@gmail.com>:
>
> > The changed code should catch 'Exception', not 'Throwable' because the
> > latter is a common ancestor of both 'Exception' and 'Error'. An
> > 'Error' must not be swallowed at any point in the system, unless you
> > are writing an app server or a JVM implementation. ;-)
>
> True enough.
>
> Does this mean that, with the change from Throwable to Exception,
> you're ok with the new implementation and it fullfills the
> expectations of your original email ?
Yes.
Regards,
Shantanu
>
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>
>
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>
>
> > Regards,
> > Shantanu
>
> > On Jan 25, 6:11 am, Ken Wesson <kwess...@gmail.com> wrote:
> >> On Mon, Jan 24, 2011 at 7:43 PM, Laurent PETIT <laurent.pe...@gmail.com>
> >> wrote:
> >> > 2011/1/25 Ken Wesson <kwess...@gmail.com>:
> >> >> Ah, I guess it may be a bit cleaner to just eschew "finally"
> >> >> altogether and close in the try and in the catch. The one thing that's
> >> >> a bit icky about that is that if the body close throws, the catch
> >> >> clause tries to close the stream again.
>
> >> > argh yes, this may be a problem ...
>
> >> There's also a bug: _ instead of _# in the close exception discarder. :)
>
> >> How's about:
>
> >> (in-ns 'clojure.core)
> >> (defmacro with-open
> >> "bindings => [name init ...]
>
> >> Evaluates body in a try expression with names bound to the values
> >> of the inits, and a finally clause that calls (.close name) on each
> >> name in reverse order."
> >> {:added "1.0"}
> >> [bindings & body]
> >> (assert-args with-open
> >> (vector? bindings) "a vector for its binding"
> >> (even? (count bindings)) "an even number of forms in binding vector")
> >> (cond
> >> (= (count bindings) 0) `(do ~@body)
> >> (symbol? (bindings 0)) `(let ~(subvec bindings 0 2)
> >> (let [res# (try
> >> (with-open ~(subvec
> >> bindings 2) ~@body)
> >> (catch Throwable t#
> >> (try
> >> (. ~(bindings 0) close)
> >> (catch Throwable _#))
> >> (throw t#)))]
> >> (. ~(bindings 0) close)
> >> res#))
> >> :else (throw (IllegalArgumentException.
> >> "with-open only allows Symbols in bindings"))))
>
> >> No double-closing and no vector. If the body throws, the exception is
> >> caught, the close is done with any close exception suppressed, and the
> >> original exception rethrown and that's it. If the body doesn't throw,
> >> we store it in res and then close. If the close throws here, the
> >> exception is allowed to propagate. Otherwise we return res.
>
> >> I've tested this with Foo and it works; modifying Foo to replace the
> >> close throw with (println "closed"), the doit throw with the integer
> >> literal 42, or both, I get:
>
> >> Both throw:
> >> #<CompilerException java.lang.Exception: doit exception
> >> (NO_SOURCE_FILE:46)>
>
> >> Close throws:
> >> #<CompilerException java.lang.Exception: close exception
> >> (NO_SOURCE_FILE:48)>
>
> >> Doit throws:
> >> closed
> >> #<CompilerException java.lang.Exception: doit exception
> >> (NO_SOURCE_FILE:46)>
>
> >> Neither throws:
> >> closed
> >> 42
>
> >> The right exception escapes if any exceptions are thrown, and "closed"
> >> is printed exactly once if close doesn't throw.
>
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