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.

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.

coolaj86

#!/bin/bash

# Usage: sudo apt-get install -yqq curl; curl -L -s https://raw.github.com/gist/4671312/ubuntu-install-media.sh | sudo bash

#alias sagi="apt-get install --yes --quiet" # normall sudo apt-get, but this is already root
#alias sagid="apt-get install --yes --quiet --download-only" # same as above
#STDOUT=/dev/stdout
#STDERR=/dev/stderr
STDOUT=/dev/null
STDERR=/dev/null

arvearve

Mathematics: What do grad students in math do all day?

by Yasha Berchenko-Kogan

A lot of math grad school is reading books and papers and trying to understand what's going on. The difficulty is that reading math is not like reading a mystery thriller, and it's not even like reading a history book or a New York Times article.

The main issue is that, by the time you get to the frontiers of math, the words to describe the concepts don't really exist yet. Communicating these ideas is a bit like trying to explain a vacuum cleaner to someone who has never seen one, except you're only allowed to use words that are four letters long or shorter.

What can you say?

swannodette

;; based on core.logic 0.8-alpha2 or core.logic master branch

(ns sudoku
  (:refer-clojure :exclude [==])
  (:use clojure.core.logic))

(defn get-square [rows x y]
  (for [x (range x (+ x 3))
        y (range y (+ y 3))]
    (get-in rows [x y])))

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

rampion

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

data Zero 
data Succ n
type One = Succ Zero

data Black

henrik

tmux cheatsheet

As configured in my dotfiles.

start new:

tmux

start new with session name:

wridgers

# Make it use C-a, similar to screen..
unbind C-b
unbind l
set -g prefix C-a
bind-key C-a last-window

# Reload key
bind r source-file ~/.tmux.conf

set -g history-limit 1000

rawbitrec

//created by Eliot Lash and Robert Muller on 10/3/10
//copyright Eliot Lash and Robert Muller 2011

//Welcome to Ye Olde Sea Pluss Pluss!

#include <iostream>
#include <string>
#include "olde.h"
#define normal