2012/9/5 Andy Fingerhut <andy.finger...@gmail.com>
> If someone types in the literal map {:a 5 :b 10 :c 13 :a -5}, what is the
> "correct thing"?
>
> Some people might be thinking the correct thing is "I want the last key
> :a's value, -5, to win always, no matter if the key :a occurs more than
> once. I never want an error for code like this."
>
> Others might be thinking "Oh, that is obviously a typo in my source code.
> I never intentionally want to specify the same key twice in any literal
> map. I want the compiler to flag that as an error so I don't have to spend
> lots of testing/debugging time to find that typo."
>
Why not _only_ throw, if the keys are provably identical? The _reader_ can
decide this on a purely syntactic basis.
So {:a 1 :a 2}, would throw. (let [a :a] {a 1 a 2}) would also throw.
(let [a1 :a a2 :a] {a1 1 a2 2}) would eliminate the duplicate key with last
one in wins behavior, as it was before. Maybe it could print a warning,
doing so.
As it happens, this catches all the obvious cases, like config-maps (where
it has already saved me once), while leaving more involved semantics alone.
Can I cast a vote that this is the most desirable behavior?
I'll start with
+1 for throwing on _syntactic_ duplicates
--
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
