I don't think that will work. for is lazy, so by the time it evals, the
code will have dropped out of the scope of with-open.
So:
(defn read-stuff-2 []
(with-open [r (java.io.BufferedReader.
(java.io.FileReader. "myfile.txt"))]
(for [line (line-seq r)]
line)))
fails with an IOException.
So, I think the OP needs:
(defn read-stuff-3 []
(with-open [r (java.io.BufferedReader.
(java.io.FileReader. "myfile.txt"))]
(doall
(for [line (line-seq r)]
line))))
or alternatively:
(defn read-stuff-4 []
(with-open [r (java.io.BufferedReader.
(java.io.FileReader. "myfile.txt"))]
(for [line (doall (line-seq r))]
line)))
I really wish there were support for this in clojure.core: both "dofor"
and "domap" would be very useful. Laziness is useful but when working
with Java objecs with state, or anything with dynamic scope liberal use
of doall is necessary which just adds extra brackets.
Phil
Jim <jimpil1...@gmail.com> writes:
> Only use 'doseq' when you don't care about the reuturn value. In other words
> only for side-effect-y code. Use 'for' instead...
>
> Jim
>
>
>
> On 21/06/13 11:17, Jay C wrote:
>> Hi, I'm fairly new to Clojure and need help with a problem. The following
>> function always returns nil, whereas it should return the value of "line"
>> (which is not nil - I've tested).
>>
>> (defn find-line-in-output [regex]
>> (with-open [rdr (reader belarc-output-filepath)]
>> (doseq [line (line-seq rdr)]
>> (if (not (nil? (re-find (re-pattern regex)
>> line)))
>> line
>> )
>> )
>> )
>> )
>>
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>
> --
--
Phillip Lord, Phone: +44 (0) 191 222 7827
Lecturer in Bioinformatics, Email: phillip.l...@newcastle.ac.uk
School of Computing Science,
http://homepages.cs.ncl.ac.uk/phillip.lord
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