Hi all,
At the risk of being labelled "the guy who always whines about
line-seq", I'm whining about line-seq again. I hit some surprising
behaviour stemming from the fact that line-seq isn't fully lazy:
(defn line-seq
"Returns the lines of text from rdr as a lazy sequence of strings.
rdr must implement java.io.BufferedReader."
[#^java.io.BufferedReader rdr]
(when-let [line (.readLine rdr)]
(cons line (lazy-seq (line-seq rdr)))))
This implementation is fully lazy:
(defn line-seq [rdr]
(lazy-seq
(when-let [line (.readLine rdr)]
(cons line (line-seq rdr)))))
but doesn't return nil on an empty sequence, which I think is why
line-seq was changed in the first place (commit
efc54c000445f8b3d8d2e75d560fa02397951598).
It seems that there's an inherent trade-off between wanting to return
nil for an empty sequence and wanting to be fully lazy, so I'm not sure
of the best way of achieving both objectives. I just thought I'd raise
the issue in case someone brighter than me has any good ideas :)
Cheers,
Mark
--
Mark Triggs
<[email protected]>
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