bobby

(ns datomic-helpers
  (:require [datomic.api     :as d]))

;;; Expose Datomic vars here, for convenience

;;; Ring middleware

(defn wrap-datomic
  "A Ring middleware that provides a request-consistent database connection and
  value for the life of a request."

daveray

Links for essays ref'd in http://blog.fogus.me/2009/03/11/seven-books/

• On the Criteria to Be Used in Decomposing Systems Into Modules – David Parnas
• A Note On Distributed Computing – Jim Waldo, Geoff Wyant, Ann Wollrath, Sam Kendall
• The Next 700 Programming Languages – P. J. Landin
• Can Programming Be Liberated from the von Neumann Style? – John Backus
• Reflections on Trusting Trust – Ken Thompson
• Lisp: Good News, Bad News, How to Win Big – Richard Gabriel
• An Experimental Evaluation of the Assumption of Independence in Multiversion Programming – John Knight and Nancy Leveson
• [Arguments and Results –

quiver

Pub/Sub pattern with PostgreSQL's LISTEN/NOTIFY command

This is a simple chat-like program using pub-sub pattern, backed by PostgreSQL's LISTEN/NOTIFY command.

Publish

publish message to foo channel from user nickname.

$ python pub.py foo nickname
PUBLISH to channel #foo

bobby

(ns user
  (:require [clojure.java.io :as io]
            [datomic.api :as d]))

(defn order-schema []
  (read-string (slurp (io/resource "schema.edn"))))

(defn start-datomic! [uri schema]
  (d/create-database uri)
  (let [conn (d/connect uri)]

lelandbatey

Description

This simple script will take a picture of a whiteboard and use parts of the ImageMagick library with sane defaults to clean it up tremendously.

The script is here:

#!/bin/bash
convert "$1" -morphology Convolve DoG:15,100,0 -negate -normalize -blur 0x1 -channel RBG -level 60%,91%,0.1 "$2"

Results

bhauman

(ns todo-server.core
  (:require
   [cljs.nodejs :as nodejs]
   [figwheel.client :as fw]))

(nodejs/enable-util-print!)

(defonce express (nodejs/require "express"))
(defonce serve-static (nodejs/require "serve-static"))
(defonce http (nodejs/require "http"))

reborg

Rich Already Answered That!

A list of commonly asked questions, design decisions, reasons why Clojure is the way it is as they were answered directly by Rich (even when from many years ago, those answers are pretty much valid today!). Feel free to point friends and colleagues here next time they ask (again). Answers are pasted verbatim (I've made small adjustments for readibility, but never changed a sentence) from mailing lists, articles, chats.

How to use:

• The link in the table of content jumps at the copy of the answer on this page.
• The link on the answer itself points back at the original post.

Table of Content

ptarjan

Scaling your API with rate limiters

The following are examples of the four types rate limiters discussed in the accompanying blog post. In the examples below I've used pseudocode-like Ruby, so if you're unfamiliar with Ruby you should be able to easily translate this approach to other languages. Complete examples in Ruby are also provided later in this gist.

In most cases you'll want all these examples to be classes, but I've used simple functions here to keep the code samples brief.

Request rate limiter

This uses a basic token bucket algorithm and relies on the fact that Redis scripts execute atomically. No other operations can run between fetching the count and writing the new count.

ghadishayban

;; differences from scheme unfold
;; even initial value is lazy
;; predicate sense reversed
;; internal state == produced value, no special mapper-fn
;; no tail-gen
(defn series
  "Produces a sequence of values.

   `f` is a function that given a value, returns the next value.
   `continue?` is a predicate that determines whether to produce

tangrammer

;; using docker-compose up, we loose the cider ability to navigate definitions with `C - .` due the source of current (docker) nrepl is under a different path `/app/src` instead of akvo-lumen local git repo
;; so the trick is to replace docker source paths by user-local-paths. 

((nil . ((eval . (defun to-local-paths (info)
		   "adapt src and .m2 docker paths to local paths"
		   (let* ((file (nrepl-dict-get info "file"))
			  (res-0 (progn
				   (replace-regexp-in-string  "/app/" (clojure-project-dir) file))))
		     (replace-regexp-in-string  "/home/akvo/.m2/"
						(concat (getenv "HOME") "/.m2/")