jboner

Latency Comparison Numbers (~2012)
----------------------------------
L1 cache reference                           0.5 ns
Branch mispredict                            5   ns
L2 cache reference                           7   ns                      14x L1 cache
Mutex lock/unlock                           25   ns
Main memory reference                      100   ns                      20x L2 cache, 200x L1 cache
Compress 1K bytes with Zippy             3,000   ns        3 us
Send 1K bytes over 1 Gbps network       10,000   ns       10 us
Read 4K randomly from SSD*             150,000   ns      150 us          ~1GB/sec SSD

andymatuschak

A composable pattern for pure state machines with effects

State machines are everywhere in interactive systems, but they're rarely defined clearly and explicitly. Given some big blob of code including implicit state machines, which transitions are possible and under what conditions? What effects take place on what transitions?

There are existing design patterns for state machines, but all the patterns I've seen complect side effects with the structure of the state machine itself. Instances of these patterns are difficult to test without mocking, and they end up with more dependencies. Worse, the classic patterns compose poorly: hierarchical state machines are typically not straightforward extensions. The functional programming world has solutions, but they don't transpose neatly enough to be broadly usable in mainstream languages.

Here I present a composable pattern for pure state machiness with effects,

lispm

; A MICRO-MANUAL FOR LISP - NOT THE WHOLE TRUTH, 1978
; John McCarthy, Artificial Intelligence Laboratory, Stanford University

; https://www.ee.ryerson.ca/~elf/pub/misc/micromanualLISP.pdf
; https://github.com/jaseemabid/micromanual

; for CL : Rainer Joswig, joswig@lisp.de

; this version runs in a Common Lisp

henrik

tmux cheatsheet

As configured in my dotfiles.

start new:

tmux

start new with session name:

isaacs

# Hello, and welcome to makefile basics.
#
# You will learn why `make` is so great, and why, despite its "weird" syntax,
# it is actually a highly expressive, efficient, and powerful way to build
# programs.
#
# Once you're done here, go to
# http://www.gnu.org/software/make/manual/make.html
# to learn SOOOO much more.

chaitanyagupta

Reader Macros in Common Lisp

This post also appears on lisper.in.

Reader macros are perhaps not as famous as ordinary macros. While macros are a great way to create your own DSL, reader macros provide even greater flexibility by allowing you to create entirely new syntax on top of Lisp.

Paul Graham explains them very well in [On Lisp][] (Chapter 17, Read-Macros):

The three big moments in a Lisp expression's life are read-time, compile-time, and runtime. Functions are in control at runtime. Macros give us a chance to perform transformations on programs at compile-time. ...read-macros... do their work at read-time.

ankurs

/**
 * @file fsm.c
 * @brief an implementation for a FSM in C, this file contains 
 * implementation of definations.
 * License GPLv3+
 * @author Ankur Shrivastava
 */

#include "fsm.h"
#include<stdlib.h>

nicebyte

#pragma once

#define DYN_ARR_OF(type) struct  { \
  type *data; \
  type *endptr; \
  uint32_t capacity; \
}

#if !defined(__cplusplus)
#define decltype(x) void*

privet-kitty

;; {}: Map literal like Clojure

;; Note:
;; 1. Equality operator is #'eql.
;; 2. {} is a literal here though it is a constructor in Clojure:
;; Clojure:
;; (:b {:a 1 :b (+ 1 2)}) => 3
;; CL:
;; (gethash :b {:a 1 :b (+ 1 2)}) => (+ 1 2)

zmactep

Alternative to the Church, Scott and Parigot encodings of data on the Lambda Calculus.

When it comes to encoding data on the pure λ-calculus (without complex extensions such as ADTs), there are 3 widely used approaches.

Church Encoding

The Church Encoding, which represents data structures as their folds. Using Caramel’s syntax, the natural number 3 is, for example. represented as:

0 c0 = (f x -> x)
1 c1 = (f x -> (f x))
2 c2 = (f x -> (f (f x)))