omasanori

(defn prime?
  "Returns true if x is prime number, false otherwise."
  [x]
  (not-any? zero?
            (map #(rem x %)
                 (range 2 (inc (/ x 2))))))

(defn prime-numbers
  "Returns a lazy seq of prime numbers."
  []

omasanori

(defn leap-year?
  "Returns true if x is leap year, false otherwise."
  [x]
  (or (zero? (rem x 400))
      (and (zero? (rem x 4))
           (not (zero? (rem x 100))))))

(defn leap-years
  "Returns a lazy seq of leap years."
  []

omasanori

(defn lcg
  "Returns a lazy seq of random numbers using linear congruential
  generators (LCGs)."
  [seed a b m]
  (map #(float (/ %))
       (drop 1
             (iterate (fn [x] (mod (+ (* a x) b) m))
             seed))))

(defn lcg-average

omasanori

(defn- diff-seq
  "Returns a lazy seq of numbers in s1 but not in s2.
  Both of s1 and s2 must be increasing monotonically."
  [s1 s2]
  (when-let [x1 (first s1)]
    (if-let [x2 (first s2)]
      (cond
        (= x1 x2) (recur (rest s1) (rest s2))
        (> x1 x2) (recur s1 (drop-while (partial > x1) s2))
        (< x1 x2) (let [[s11 s12] (split-with (partial > x2) s1)]

omasanori

(ns generate-boundary)

(defn- char-range
  "Returns a lazy seq of characters between `start` and `end`.
  Unlike clojure.core/range, `end` is included in the results.
  e.g. (= \9 (last (char-range \0 \9)))"
  [start end]
  (map char (range (int start) (inc (int end)))))

(def ^:dynamic *characters*

omasanori

;;; bf.clj --- A Brainfuck interpreter written in Clojure
;; The idea to implement loop instructions without waste of stack
;; is borrowed from a interpreter by Blake Williams, available at
;; https://github.com/BlakeWilliams/Clojure-Brainfuck

;;; Data Constructors and Manipulators
;; TODO(omasanori): Consider writing a macro to remove duplication of code.
(defn valid-address?
  "Returns true if `address` is valid, otherwise false."
  [address]

omasanori

;;; See also
;; http://d.hatena.ne.jp/mkut/20111226/1324907006
;; http://blog.livedoor.jp/dankogai/archives/51763038.html

;; My straightforward but naive solution.
(defn naive-map-between
  [f coll]
   (lazy-seq
     (let [[x y] coll]
       (when (and x y)

omasanori

PyPyのGCに挑戦した……けど……な話

これは[Garbage Collection Advent Calendar 2012][gcac2012]の20日目の文書として @omasanori がPyPyのGCを解説する……はずでしたが、期日までに理解しきれませんでした。すみません。

そこで、ここでは私が現時点でどこまで理解できたか、これからどこを読んでいくか、という途中経過を記すことにします。GC初心者視点なのでGC上級者には物足りない文章になっていると思います。

はじめに

[PyPy][pypy]はRestricted Python (RPython)と呼ばれるPythonのサブセットを中心としたインタプリタ実装ツールキットと、それを利用したPythonの処理系です。Pythonの処理系としての印象が強いですが、RPythonとツールキットの部分は他のインタプリタを実装するために利用することも可能です。

omasanori

cfg: build triple x86_64-unknown-linux-gnu
cfg: host triples x86_64-unknown-linux-gnu
cfg: target triples x86_64-unknown-linux-gnu
cfg: host for x86_64-unknown-linux-gnu is x86_64
cfg: os for x86_64-unknown-linux-gnu is unknown-linux-gnu
cfg: using gcc
cfg: no node found, omitting docs
cfg: no llnextgen found, omitting grammar-verification
compile_and_link: x86_64-unknown-linux-gnu/stage0/lib/rustc/x86_64-unknown-linux-gnu/bin/rustc
error: linking with `cc` failed with code 1

omasanori

fn seq_lt<A: Eq + Ord, T: Iterator<A>>(mut a: T, mut b: T) -> bool {
    loop {
        match (a.next(), b.next()) {
            (None, None) => return false,
            (None, _   ) => return true,
            (_,    None) => return false,
            (Some(x), Some(y)) => if !x.eq(&y) { return x.lt(&y) }
        }
    }
}