#pelure

Welcome to another stellar issue of Clojure Weekly! This one is just before my talk at EuroClojure. Here I collect a few links, normally 4/5 urls, pointing at articles, docs, screencasts, podcasts and anything else that attracts my attention in the clojure-sphere. I add a small comment so you can decide if you want to look at the whole thing or not. That’s it, enjoy!

lazy evaluation - Clojure: rest vs. next - Stack Overflow Nice discussion on StackOverflow about next VS rest. It can get quite philosophical and reading the sources is not helping a lot (I could only track that ASeq.rest() is calling next() inside but each collection has a different implementation of this). One sure thing is that to return nil next needs to look ahead and realise at least the next element or the next chunk of a sequence. So rest is more lazy than next.

clojure-compiler/src/net/n01se/clojure_compiler.clj at master · Chouser/clojure-compiler Another bit of Clojure history. Chris Houser is one of the protagonist of the Clojure scene and one of the earliest receptor of Rich's ideas about the future of Clojure. Apart from his very good book (manning.com/fogus) he should also be credited for a couple of important early attempts: ClojureScript and Clojure in Clojure. Although his work didn't end up being part the current related efforts, it is stil inspirational. Linked here is a clojure compiler in clojure from 2009. If you look at the bottom, it is tested by parsing the compiler itself.

Pelure - Shell Scripting in Clojure with Pallet github.com/pallet/stevedore is an internal clojure DSL that emits bash shell scripting. Personally I don't write a lot of shell scripting, just the right amount when needed and when that happens I'm definitely going to look up yet again how I need to implement a condition or a loop. No more with Stevedore. I just write my favourite Clojure with some imperative style and voila, I can output shell scripting. Maybe that could be the base skeleton to start with. It allows advanced "macro style" scripting, with quoting pure Clojure to express some more complicated stuff that doesn't necessarily belong to the DSL language. Cool.

ClojureDocs - clojure.core/group-by And just when you were abandoning all further attempts and accepted to use a fairly understandable "reduce" here comes the group-by. The name speaks quite clearly: give it a list of maps and a key and group-by will group those maps by the value of that key. The reduce is still there in the sources but handed gracefully and with an eye on performances by the standard library. If you open the sources you'll see that it is assoc! a transient map to build up results and make it persistent at the end.

More Open-Source Clojure Systems, Please uSwitch is a neat Clojure shop in London and they recently decided to share some of the goodies they are producing over there. This post also illustrates a few of the Clojure infrastructure best practices and tools they adopted, including a component system, riemann monitoring and much more. The post is also an invite for all the other Clojure shops to open-source more of their work. I couldn't agree more. At the Dailymail I started taking care of this part a little more and open sourced the first of a series of libraries/tools that are part of our daily practice. But we still have a lot to do in this direction. Stay tuned and share more.

You’d need to be committed. That entails posting more than just a few photos every day. You need to reblog everytime you see one that fits our blogs theme. 

Other than that there’s really nothing. We could just use some more helpers!