fogus

Latency numbers every programmer should know

L1 cache reference ......................... 0.5 ns
Branch mispredict ............................ 5 ns
L2 cache reference ........................... 7 ns
Mutex lock/unlock ........................... 25 ns
Main memory reference ...................... 100 ns             
Compress 1K bytes with Zippy ............. 3,000 ns  =   3 µs
Send 2K bytes over 1 Gbps network ....... 20,000 ns  =  20 µs
SSD random read ........................ 150,000 ns  = 150 µs

Read 1 MB sequentially from memory ..... 250,000 ns = 250 µs

fogus

(defun pretty-lambdas ()
  "Show glyph for lower-case Greek lambda (λ) wherever 'lambda' appears."
  (font-lock-add-keywords
    nil
    `(("(\\(lambda\\>\\)"
       (0
         (progn
           (compose-region
             (match-beginning 1)
             (match-end 1)

fogus

: throw drop ;
: tuck swap over ;


: car! ( v a - ) ! ; 
: cdr! ( v a - ) cell+ ! ; 
: car@ ( a - v ) @ ;
: cdr@ ( a - v ) cell+ @ ;
: cons ( k v - a ) swap 2 cells allocate throw tuck ! tuck ! ;
: cons0 ( - a ) 0 0 cons ;

fogus

----------------------------------------------------------------------------------------------------
--- Making Lua look like Prolog:
---
--- Let's use metatables for something other than emulating prototype-based OO. By making the
--- __index metamethod create values for undefined things, we can make Lua look like Prolog!
--- We create empty tables for anything starting with a capital letter, functions that populate
--- those tables for lowercase things (to assign relationships) and if a name begins with "is_"
--- then it becomes a function that queries those tables.
----------------------------------------------------------------------------------------------------

fogus

;   Copyright (c) Rich Hickey. All rights reserved.
;   The use and distribution terms for this software are covered by the
;   Eclipse Public License 1.0 (http://opensource.org/licenses/eclipse-1.0.php)
;   which can be found in the file epl-v10.html at the root of this distribution.
;   By using this software in any fashion, you are agreeing to be bound by
;   the terms of this license.
;   You must not remove this notice, or any other, from this software.

(set! *warn-on-reflection* true)

fogus

function fibonnaci(n, done) {
    if (n === 1 || n === 2) {
        done(1);
    } else {
        process.nextTick(function() {
            fibonnaci(n - 1, function(val1) {
                process.nextTick(function() {
                    fibonnaci(n - 2, function(val2) {
                        done(val1 + val2);
                    });

fogus

(defn neighbours [[x y]]
  (for [dx [-1 0 1] dy (if (zero? dx) [-1 1] [-1 0 1])]
    [(+ dx x) (+ dy y)]))

(defn step [cells]
  (set (for [[loc n] (frequencies (mapcat neighbours cells))
             :when (or (= n 3) (and (= n 2) (cells loc)))]
         loc)))

(def board #{[2 1] [2 2] [2 3]})

fogus

#!/usr/bin/env ruby

# the stack
$stack = []
def pop() $stack.pop || ufe end
def push(f) $stack<<f end
# poor man's Exception class
def ufe() raise("Stack underflow") end

# lambda constructor helpers

fogus

(defun null. (x)
      (eq x '()))
 
(defun and. (x y)
  (cond (x (cond (y 't) ('t '())))
        ('t '())))
 
(defun not. (x)
  (cond (x '())
        ('t 't)))

fogus

def ∑(r:Range)(f:Int =>Int)=r.reduceLeft(_+ f(_))
def ∏(r:Range)(f:Int =>Int)=r.reduceLeft(_* f(_))

// And now we can write:

val s= ∑(1 to 100)(x=>x^2)
val p= ∑(1 to 100 by 2)(x=>x^2)
val y= ∏(1 to 30 by 3)(_)