avl-rb-clojure-intro

1.1 What is Clojure? slide

A Lisp
- Homoiconic - Code as data
- Functional
  - Not Object Oriented
  - built around immutable data structures
Runs on the JVM
- Embraces Java
ClojureCLR, ClojureScript, clojure-py are alt. impls.

1.1.1 5 years old notes

1958
s-expressions (symbolic)

1.2 Parts of Clojure slide

very little syntax

1.2.1 Truthiness slide

nil and false are false
true and everything else is true, including empty lists
same as ruby

1.2.2 Primitives - Strings slide

Just java strings

"I'm a string"

1.2.2.1 No string interp notes

1.2.3 Primitives - Characters slide

Just java characters

\a \b \x

1.2.3.1 but w/o single quotes notes

1.2.4 Primitives - Numbers slide

42   ;; long
42N  ;; clojure.lang.BigInt
4.2  ;; double
4.2M ;; java.math.BigDecimal
22/7 ;; ratio

1.2.5 Primitives - Symbols slide

names of things

str
println
clojure.string/split

1.2.6 Primitives - Keywords slide

identifiers, offer fast equality
often used as map keys
are functions of maps

:foo
:what-is-this-thing-in-my-hair?
:some.namespace/bar

(:key {:key "value"}) ;; => "value"

1.2.7 Collections - Lists slide

implemented as a linked list
have special eval semantics

(1 2 3 4)

(str "a" "b" "c")

1.2.7.1 head is fast notes

1.2.8 Collections - Vectors slide

an array
generally used unless list semantics or performance needed
functions of index

[1 2 3 4]

([1 2 3 4] 1) ;; => 2

1.2.8.1 tail is fast notes

1.2.9 Collections - Maps slide

analogous to a Ruby Hash
functions of keys

{:a :b, :c :d}

({:key "value"} :key) ;; => "value"

1.2.10 Collections - Sets slide

functions of their members

#{1 2 3 4}

(#{"yes" "no"} "yes")   ;; => "yes"
(#{"yes" "no"} "maybe") ;; => nil

1.3 Immutability slide

(def x {:a :b})
(assoc x :c :d) ;; => {:a :b, :c :d}
x               ;; => {:a :b}

(def y [1 2 3])
(conj y 4)      ;; => [1 2 3 4]
y               ;; => [1 2 3]

1.3.1 def creates a 'var' notes

internal structure is shared
makes concurrency easier

1.4 Lazy Sequences slide

values in the sequence aren't realized until needed
allows working with large/infinite datasets

(take 10 (range)) ;; => (0 1 2 3 4 5 6 7 8 9)

1.4.1 range is infinite notes

take itself returns a lazy sequence

1.5 Function Definition slide

named

(defn ham-is-good [a b]
  (println (if (or (= a "ham")
                   (= b "ham"))
             "Ham goes good with anything!"
             (str a " and " b "? Grody!"))))

1.5.1 this is just data notes

1.6 Function Definition slide

anonymous - lambdas

(fn [v]
  (println "I got" v))

#(println "I got" %)

1.6.1 compare to ruby blocks notes

1.7 Reference Types slide

allow for controlled mutability
can only be manipulated via special functions
mutation occurs within a transaction
must be explicitly dereferenced

(def an-atom (atom 0))

(swap! an-atom inc)

@an-atom ;; => 1

1.7.1 STM & MVCC notes

atoms - single changing value
agents - asynchronous update of a single value
refs - mutliple coordinated changing values; explicit (dosync)

1.8 Let & Desctructuring slide

bind values in a closure

(let [full-name (some-name-producing-function)
      [first-name last-name] 
        (split full-name #" ")]
  (println full-name "splits into" 
           first-name last-name))

1.8.1 values only bound inside let notes

introduces destructuring
aka structural binding

1.9 Let & Destructuring slide

(let [point [123 456]
      [x-coord y-coord] point]
  (defn draw-something
    [height width 
     {:keys [color opacity] :as options}]
    (draw-square x-coord y-coord height 
                 width color opacity)
    (something-else-that-wants-options options)))

1.10 REPL slide

the Read-Eval-Print Loop

1.10.1 think irb notes

1.11 Demo! slide

1.12 Pros/Cons slide

pros:
- write code with less errors
- bend your brain
- access to all Java libraries
- safe(r) concurrency
cons:
- have to learn Java as well
- young ecosystem

1.13 Who uses Clojure? slide

Twitter
Heroku
Datomic
World Singles
Sonian
Runa
Me! (therefore Red Hat)

1.14 Resources slide

Clojure Koans - https://github.com/functional-koans/clojure-koans
4clojure - http://www.4clojure.com/
#clojure on freenode
clojure@googlegroups.com
books
- Programming Clojure - Stuart Halloway
- Joy of Clojure - Michael Fogus & Chris Houser

avl-rb-clojure-intro

Table of Contents

1 Intro to Clojure slide

1.1 What is Clojure? slide

1.1.1 5 years old notes

1.2 Parts of Clojure slide

1.2.1 Truthiness slide

1.2.2 Primitives - Strings slide

1.2.2.1 No string interp notes

1.2.3 Primitives - Characters slide

1.2.3.1 but w/o single quotes notes

1.2.4 Primitives - Numbers slide

1.2.5 Primitives - Symbols slide

1.2.6 Primitives - Keywords slide

1.2.7 Collections - Lists slide

1.2.7.1 head is fast notes

1.2.8 Collections - Vectors slide

1.2.8.1 tail is fast notes

1.2.9 Collections - Maps slide

1.2.10 Collections - Sets slide

1.3 Immutability slide

1.3.1 def creates a 'var' notes

1.4 Lazy Sequences slide

1.4.1 range is infinite notes

1.5 Function Definition slide

1.5.1 this is just data notes

1.6 Function Definition slide

1.6.1 compare to ruby blocks notes

1.7 Reference Types slide

1.7.1 STM & MVCC notes

1.8 Let & Desctructuring slide

1.8.1 values only bound inside let notes

1.9 Let & Destructuring slide

1.10 REPL slide

1.10.1 think irb notes

1.11 Demo! slide

1.12 Pros/Cons slide

1.13 Who uses Clojure? slide

1.14 Resources slide