On Jun 18, 2010, at 10:09 PM, Mark Engelberg wrote:
An idea to consider:
How about keeping the arbitrary-precision default, but add a loop'
construct to the family of +',-',*',inc', and dec' for primitive
optimization? The loop' construct would bind primitive literals,
whereas the loop construct would keep the literals boxed, so people
who don't want to analyze types rigorously in their loop/recur
constructs won't get mismatch errors.
I see that using primitive literals by default in loop/recur offers
speed benefits for the common case (recur type matches the
loop-declared type), but I worry about how hard it might be to analyze
and make sure that I'm always recurring with a type that exactly
matches what is in the loop.
Did you try it? The compiler does that analysis and reports any
mismatch:
user=> (defn foo [] (loop [x 42] (recur 4.2)))
NO_SOURCE_FILE:2 recur arg for primitive local: x is not matching
primitive, had: double, needed: long
user=> (defn foo [] (loop [x 42] (recur false)))
NO_SOURCE_FILE:5 recur arg for primitive local: x is not matching
primitive, had: java.lang.Boolean, needed: long
user=> (defn foo [] (loop [x 4.2] (recur (meta #'first))))
NO_SOURCE_FILE:15 recur arg for primitive local: x is not matching
primitive, had: java.lang.Object, needed: double
Any other ideas on how to solve the problem of mismatch errors for
"casual coders"?
Those could become hard errors again. But there are legitimate correct
cases that would then need annotation:
(defn foo [] (loop [x 42] (recur (:y z))))
Rich
--
You received this message because you are subscribed to the Google
Groups "Clojure" group.
To post to this group, send email to clojure@googlegroups.com
Note that posts from new members are moderated - please be patient with your
first post.
To unsubscribe from this group, send email to
clojure+unsubscr...@googlegroups.com
For more options, visit this group at
http://groups.google.com/group/clojure?hl=en
