Re: doall vs. dorun

[Stephen C. Gilardi]

On Jan 20, 2009, at 5:32 PM, Mark Volkmann wrote:

Here's one:

(defn read-my-file []
(with-open [reader (BufferedReader. (FileReader. "my-file.txt"))]
  (doall (line-seq reader))))

"line-seq" returns a lazy sequence, but you have to consume that
sequence before "with-open" closes the file.

How is it different if you change "doall" to "dorun"? According to
their doc strings, they both "can be used to force any effects. Walks
through the successive rests of the seq"

Here's a simpler example:

        user=> (doall (map #(do (prn %) %) [1 2 3]))
        1
        2
        3
        (1 2 3)
        user=> (dorun (map #(do (prn %) %) [1 2 3]))
        1
        2
        3
        nil
        user=>

(Note the difference in return value.)

--Steve

Using doall will cause read-my-file to return a seq of all the lines. dorun will return nil.

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