cgrand

;; simple stats computed using xforms transducers
=> (require '[net.cgrand.xforms :as x])
=> (into {}
     (x/by-key #(> % 0.5)
       (x/transjuxt {:min x/min :max x/max :avg x/avg :sd x/sd}))
     (repeatedly 1e6 rand))
{false
 {:min 1.0036018363024368E-6,
  :max 0.4999987525112054,
  :avg 0.2502046186242099,

cgrand

;; not quite an apple-to-apple comparison (merge3 and into) but the order of magnitude is correct:
;; into: 5µs
;; merge3: 17ns (yes, ns not µs)
;;
;; this huge difference comes from the fact that merge3 runtime varies with the number of modified keys (here 1)
;; while into runtime varies with the number of keys. 

user=> (def e clojure.lang.PersistentHashMapKVMono/EMPTY)
(defn merge3 [anc a b fix] (clojure.lang.PersistentHashMapKVMono/merge anc a b fix))
#'user/e

jackrusher

(defn branch
  "A recursive branching tree structure with half-cylinder flowers."
  [level]
  (if (= 0 level)
    [(length 1.5) cylinder]
    [(angle (fn [_] (m/random 3 5))) ry-
     (length (fn [t] (* (m/random 0.75 1.5) (or (:last-length t) 1.5))))
     (map (fn [[a b]] (concat (take 8 (cycle [a b])) (branch (dec level))))     
          [[ry line] [ry- line] [rx line] [rx- line]])]))

cgrand

;; pagerank in podwerkeg
(reduce (fn [ranks _]
          (keg/rdd (keg/join links ranks)
            (x/for [[page-id [page-links rank]] %
                    dest page-links]
              [dest (/ rank (count page-links))])
            (keg/by-key (x/reduce +) (map #(+ 0.15 (* 0.85 %))))))
  (keg/rdd links (keg/by-key (map (constantly 1)))) (range 10))

postspectacular

;; Tetrahedron intersection based on this paper & algorithm:
;; http://vcg.isti.cnr.it/Publications/2003/GPR03/fast_tetrahedron_tetrahedron_overlap_algorithm.pdf
;;
;; Unlike original algorithm this implementation produces correct
;; results regardless of the orientation/ordering of points defining
;; the two tetrahedra. This is achieved via the orient-tetra function,
;; which ensures the correct ordering of vertices for this algorithm
;; to function properly.
;;
;; Implementation extracted from upcoming geometry library

cgrand

;; Clojure 1.5.1
=> ; coll (fn [f acc]) renvoie (reduce f acc coll)
=> ; coll (fn [f init]) renvoie (reduce f init coll)
=> (defn fnil [f init] init)
WARNING: fnil already refers to: #'clojure.core/fnil in namespace: cljug.core, being replaced by: #'cljug.core/fnil
#'cljug.core/fnil
=> (reduce + 0 nil)
0
=> (fnil + 0)
0