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.

jameshfisher

Having read a few proofs that the halting problem is undecidable, I found that they were quite inaccessible, or that they glossed over important details. To counter this, I've attempted to re-hash the proof using a familiar language, JavaScript, with numerous examples along the way.

This famous proof tells us that there is no general method to determine whether a program will finish running. To illustrate this, we can consider programs as JavaScript function calls, and ask whether it is possible to write a JavaScript function which will tell us

vedang

(ns example.hystrix.redis
  (:require [com.netflix.hystrix.core :as hystrix]
            [taoensso.carmine :as car :refer [wcar]])
  (:refer-clojure :exclude [time get set key keys type sync sort eval]))


(def server-spec {:spec {:host "127.0.0.1"
                         :port 6379}
                  :pool {:max-active 8}})

willurd

Each of these commands will run an ad hoc http static server in your current (or specified) directory, available at http://localhost:8000. Use this power wisely.

Discussion on reddit.

Python 2.x

$ python -m SimpleHTTPServer 8000

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

paulmillr

Most active GitHub users (git.io/top)

The list would not be updated for now. Don't write comments.

The count of contributions (summary of Pull Requests, opened issues and commits) to public repos at GitHub.com from Wed, 21 Sep 2022 till Thu, 21 Sep 2023.

Because of GitHub search limitations, only 1000 first users according to amount of followers are included. If you are not in the list you don't have enough followers. See raw data and source code. Algorithm in pseudocode:

githubUsers