On Oct 16, 2008, at 7:29 AM, Rich Hickey wrote:
> Another semantic marker here is 'do'. do in Clojure implies side-
> effects. Since you can't uppercase a string by side effect, doto isn't
> the right tool for this job.
Neat.
I explored the "do..." marker a little with Clojure:
- user=> (filter #(re-matches #"do.*" %) (map #(-> % first name) (ns-
publics 'clojure)))
("dorun" "doseq" "dosync" "dotimes" "doubles" "doto" "double-array"
"doall" "double" "doc")
The "do implies a side-effect emphasis" pattern holds for dorun,
doseq, dosync, dotimes, doto, and doall.
- The doc for the function "repeatedly" mentions "presumably with
side effects", but it doesn't begin with "do".
- The special form "do" is just about grouping, independent of side
effects.
I recently changed the clojure.contrib.sql/with-results macro to
remove a "doseq" call. Now it just provides the sequence of results
and lets the caller decide what to do with it which is a lot more
flexible.
Coming from an imperative programming mindset, I find that imperative/
side-effecting is often the first thing that occurs to me. When I work
on the code to make it more functional, it's pretty much uniformly an
improvement in how flexible and composable it is.
As a very welcome bonus, I'm also finding it's a lot more fun!
--Steve
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