Add =?

[amalloy]

I added a function named =? which mirrors the EquivPred stuff that Rich added to clojure the other day. I ran a benchmark on some simple tasks using =? compared to plain =, and it's around 25% faster for the particular use case I tried. Test code:

(let [objs [1 :x [2] "foo"]]
  (bench
   (doseq [x objs
           :let [cmp (=? x)]
           y objs]
     (cmp y))))

Evaluation count : 52415460 in 60 samples of 873591 calls.
Execution time mean : 1.148325 us
Execution time std-deviation : 23.104390 ns
Execution time lower quantile : 1.097617 us ( 2.5%)
Execution time upper quantile : 1.181024 us (97.5%)

Found 14 outliers in 60 samples (23.3333 %)
low-severe 3 (5.0000 %)
low-mild 9 (15.0000 %)
high-mild 2 (3.3333 %)
Variance from outliers : 9.3567 % Variance is slightly inflated by outliers

(let [objs [1 :x [2] "foo"]]
  (bench
   (doseq [x objs
           y objs]
     (= x y))))

Evaluation count : 40467780 in 60 samples of 674463 calls.
Execution time mean : 1.492065 us
Execution time std-deviation : 12.754895 ns
Execution time lower quantile : 1.476391 us ( 2.5%)
Execution time upper quantile : 1.523519 us (97.5%)

Found 2 outliers in 60 samples (3.3333 %)
low-severe 2 (3.3333 %)
Variance from outliers : 1.6389 % Variance is slightly inflated by outliers