jkk

;;
;; NS CHEATSHEET
;;
;; * :require makes functions available with a namespace prefix.
;;
;; * :use makes functions available without a namespace prefix
;;   (i.e., refers functions to the current namespace).
;;
;; * :import refers Java classes to the current namespace.
;;

mfikes

First start up the REPL by issuing this command:

clj -Sdeps '{:deps {github-mfikes/e00202b2de7cc2352fedcf92b1fe60dc {:git/url "https://gist.github.com/mfikes/e00202b2de7cc2352fedcf92b1fe60dc" :sha "68ef581813e08a92bd52e7beeea1535ab7b3337f"}}}' -m cljs.main -i @index.cljs -r

Once the REPL is waiting for the browser to connect, if it doesn't automatically, open http://localhost:9000 in your browser.

You will now be running Bocko. The following forms evaluated in the REPL will draw an American flag.

city41

This is the example that comes with the reagent template converted to use HTML5 based history. This means there are no # in the urls.

I just got this working, so there might be better approaches

The changes are

• use goog.history.Html5history instead of goog.History
• listen to clicks on the page, extract the path from them, and push them onto the history
• listen to history changes, and have secretary do its thing in response

mchambers

// Let's define a basic Swift class.
class Fruit {
    var type=1
    var name="Apple"
    var delicious=true
}

// We can get at some info about an instance of an object using reflect(), which returns a Mirror.
reflect(Fruit()).count
reflect(Fruit())[1].0

alandipert

ClojureScript macros: kinda, sorta, not really.

ClojureScript does not have a standalone macro system. To write ClojureScript macros, one must write them in Clojure and then refer to them in ClojureScript code. This situation is workable, but at a minimum it forces one to keep ClojureScript code and the macros it invokes in separate files. I miss the locality of regular Clojure macros, so I wrote something called maptemplate that gives me back some of what I miss. The technique may be useful in other scenarios.

Problem

Suppose you're wrapping functionality in another namespace or package so that you can have your own namespace of identically named but otherwise decorated functions:

ClojureScript:

seabre

(ns three.demo)
(def THREE js/THREE)
(def camera (THREE.PerspectiveCamera. 75 (/ (.-innerWidth js/window)
                                 (.-innerHeight js/window)) 1 10000))
(set! (.-z (.-position camera)) 1000)
(def scene (THREE.Scene.))
(def geometry (THREE.CubeGeometry. 200 200 200))
(def obj (js/Object.))
(set! (.-color obj) 0xff0000)
(set! (.-wireframe obj) true)

schnell18

sudo rm -fr /Library/Java/JavaVirtualMachines/jdk-9.jdk/
sudo rm -fr /Library/Internet\ Plug-Ins/JavaAppletPlugin.plugin
sudo rm -fr /Library/PreferencePanes/JavaControlPanel.prefPane

gititGoro

Setting up a private ethereum blockchain for development and pointing your wallet at it

Ethereum tutorials all advise downloading the Mist wallet and beginning dev. The only problem is that the testnet and real blockchain are huge and take hours to download. What follows is a recipe for quickly setting up a small blockchain and pre-mining it with some test ethereum

The following is done in Linux but will work in MacOS and should have equivalent command line options in Windows. Where I don't give detailed instructions, it's because a quick google search will fill in the blanks.

Install geth https://github.com/ethereum/go-ethereum/wiki/geth

install Mist https://github.com/ethereum/mist/releases

mfikes

ClojureScript master now has cljs.core/eval. This delegates to cljs.core/*eval* which, by default throws, but you can bind it to any implementation that can compile and evaluate ClojureScript forms.

If you require the cljs.js namespace (which is the main support namespace for self-hosted ClojureScript), then cljs.core/*eval* is set to an implementation that uses self-hosted ClojureScript for this capability. This means that all self-hosted ClojureScript environments will now have a first-class eval implementation that just works. For example, Planck master:

$ planck -q
cljs.user=> (eval '(+ 2 3))
5

chanks

Turning PostgreSQL into a queue serving 10,000 jobs per second

RDBMS-based job queues have been criticized recently for being unable to handle heavy loads. And they deserve it, to some extent, because the queries used to safely lock a job have been pretty hairy. SELECT FOR UPDATE followed by an UPDATE works fine at first, but then you add more workers, and each is trying to SELECT FOR UPDATE the same row (and maybe throwing NOWAIT in there, then catching the errors and retrying), and things slow down.

On top of that, they have to actually update the row to mark it as locked, so the rest of your workers are sitting there waiting while one of them propagates its lock to disk (and the disks of however many servers you're replicating to). QueueClassic got some mileage out of the novel idea of randomly picking a row near the front of the queue to lock, but I can't still seem to get more than an an extra few hundred jobs per second out of it under heavy load.

So, many developers have started going straight t