Java – How independent is Clojure from Java

clojurejavalibraries

I am quite new to the Clojure world. I appreciate the fact that one has easy access to all Java libraries via Clojure interop features, but I was wondering how much Clojure stands on its own legs.

Of course there are some platforms, like Android, where interoperability with Java will always be required, because the core libraries are written or exposed in Java. Moreover, since Clojure strings are Java strings, I expect string manipulation libraries to be a wrapper on the Java String methods.

But for other tasks I see no reason why native Clojure libraries couldn't be developed. Think of Http, date manipulation, XML parsing, templating, JSON serialization and deserialization, OAuth, math libraries and so on.

So my question is:

How far has Clojure come to become independent of the Java ecosystem? Does it have its own idiomatic libraries for most of these and other tasks?

Best Answer

Clojure is becoming more and more independent of Java libraries as its code base grows and naturally diversifies. A major strength of Clojure is that it can call Java, so to see Clojure code in the future that doesn't use java would be unlikely. That being said, I have done a good deal of development w/o calling Java libs(command line args, basic text minupulation, etc). Here's a list of pure clojure libraries: http://www.clojure-toolbox.com/

Related Solutions

Clojure: vars, atoms, and refs (oh the)

Use Refs for synchronous, coordinated and shared changes.
Use Agents for asynchronous, independent and shared changes.
Use Atoms for synchronous, independent and shared changes.
Use Vars for isolated changes.

EDIT
The links you posted are highly important to read, however I also recommends this: Software Transactional Memory

Keep in mind that aborted transactions will be replayed. What does this mean?
It means that the code inside dosync could be executed a couple of times, so you need to be careful the code should be side effects free.

One use of agents is to have a controlled side effects. Consider this:

(dosync
  (send log-agent message args)
  (alter reference function))

The STM will hold all of the actions needed to be sent to agents until succeed.

What is difference between atoms and agents?
Updates to agents will happen asynchronously at some point of the future, updates to atoms will happened immediately.

Atoms and agents don't need to run inside a transaction, refs should be (coordinated changes, remember?)

Understanding clojure keywords

the & in (defn full-name [& {first :first last :last}] indicates that all the remaining arguments should be gathered into a single collection. the map destructuring form following the & then takes the map created by the & apart again.

(defn full-name [& {first :first last :last}]...)
(full-name :first "Tom" :last "Brennan")

without the & becomes

 (defn full-name [{first :first last :last}]...)
(full-name {:first "Tom" :last "Brennan"})

for your other question: symbols and keywords implement the function interface so they can be called just like any other Clojure function. when called as a function they look themselves up in their argument which they expect to be a map (or something implementing the appropriate interface)

Best Answer

Related Solutions

Clojure: vars, atoms, and refs (oh the)

Understanding clojure keywords

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