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

henrik

tmux cheatsheet

As configured in my dotfiles.

start new:

tmux

start new with session name:

lazywithclass

Looking at the most beautiful program ever written - part 1

I am going to have a look at what William Byrd presented as The most beautiful program ever written.

Beauty here refers to computer programs, specifically about Lisp. There might be errors as this is something I wrote to make sense of that interpreter, proceed at your own risk.

Thanks a lot to Carl J. Factora for the help.

The program

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.

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.

nicebyte

#pragma once

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

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

rampion

{-# LANGUAGE GADTs #-}
{-# LANGUAGE RankNTypes #-}
{-# LANGUAGE StandaloneDeriving #-}
module RedBlackTree where

data Zero 
data Succ n
type One = Succ Zero

data Black

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,

swatson555

/* Heap based virtual machine described in section 3.4 of Three Implementation Models for Scheme, Dybvig
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <assert.h>

char token[128][32];

brunobord

taken from

The system

The minisystem goes like this:

• Say what you do and roll a number of d6s.
• If the sum of your roll is higher than the opposing roll (either another player or the DM), the thing you wanted to happen, happens.
• The number of the d6s you roll is determined by the level of skill you have.