Intro to Clojure - Week 1

Week 1 slides of Introduction to Clojure @ UNB, Fall 2013

Transcript

1. Ian Bishop @ianbishop
2. Studied at UNB (CS/Math) Work at UserEvents Open Source (Official Clojure ZMQ) (Unofficial Clojure LMAX Disruptor)
3. Modern dialect of Lisp Created by Rich Hickey in 2007 General purpose functional language Runs on a number of platforms (JVM, CLR, Javascript)
4. Modern dialect of Lisp Created by Rich Hickey in 2007 General purpose functional language Runs on a number of platforms (JVM, CLR, Javascript)
5. baby
6. Invented in 1958 by John McCarthy Second oldest modern programming language Introduced fundamental ideas of modern programming Tree Data Structures Garbage Collection Dynamic Typing Conditionals Recursion Higher-order functions
7. the greatest single programming language ever designed Alan Kay, creator of Smalltalk & Object Oriented programming
8. the greatest single programming language ever designed Alan Kay, creator of Smalltalk & Object Oriented programming
9. Some may say Ruby is a bad rip- off of Lisp or Smalltalk, and I admit that. But it is nicer to ordinary people Matz, creator of the Ruby programming language
10. Some may say Ruby is a bad rip- off of Lisp or Smalltalk, and I admit that. But it is nicer to ordinary people Matz, creator of the Ruby programming language
11. any sufficiently complicated C or Fortran program contains an ad hoc informally- specified bug-ridden slow implementation of half of Common Lisp Philip Greenspun
12. any sufficiently complicated C or Fortran program contains an ad hoc informally- specified bug-ridden slow implementation of half of Common Lisp Philip Greenspun
13. Lisp is worth learning for the profound enlightenment experience you will have when you finally get it; that experience will make you a better programmer for the rest of your days, even if you never actually use Lisp itself a lot. Eric Raymond, Essayist & Open Source demigod
14. Lisp is worth learning for the profound enlightenment experience you will have when you finally get it; that experience will make you a better programmer for the rest of your days, even if you never actually use Lisp itself a lot. Eric Raymond, Essayist & Open Source demigod
15. I suppose I should learn Lisp, but it seems so foreign Paul Graham, Author of “On Lisp” & creator of Y Combinator
16. I suppose I should learn Lisp, but it seems so foreign Paul Graham, Author of “On Lisp” & creator of Y Combinator
17. (f arg0 arg1 arg2)
18. (+ 1 2 3)
19. (+ 1 2 3) => 6
20. (list 1 2 3)
21. (list 1 2 3) => (1 2 3)
22. (if (= 1 1) (list 1 2 "foo") (list 1 2 "bar"))
23. (if (= 1 1) (list 1 2 "foo") (list 1 2 "bar")) => (1 2 "foo")
24. (lambda (x) (+ x 1))
25. ((lambda (x) (+ x 1)) 5)
26. ((lambda (x) (+ x 1)) 5) => 6
28. (* 2 (+ 3 4))
29. Abstract syntax tree is isomorphic to the textual representation of the language
30. Abstract syntax tree is isomorphic to the textual representation of the language
31. Abstract syntax tree is isomorphic to the textual representation of the language
32. Abstract syntax tree is isomorphic to the textual representation of the language
33. …
34. code = data
35. code = data data = code
37. Reducing incidental complexity is a primary focus of Clojure. For example, mutable state is an incidental complexity. The mechanics of it seem simple, or at least familiar, but the reality is quite complex. So, Clojure makes immutable data the default. Rich Hickey, creator of Clojure
38. Reducing incidental complexity is a primary focus of Clojure. For example, mutable state is an incidental complexity. The mechanics of it seem simple, or at least familiar, but the reality is quite complex. So, Clojure makes immutable data the default. Rich Hickey, creator of Clojure
39. Reducing incidental complexity is a primary focus of Clojure. For example, mutable state is an incidental complexity. The mechanics of it seem simple, or at least familiar, but the reality is quite complex. So, Clojure makes immutable data the default. Rich Hickey, creator of Clojure
40. cat.setName("Felix"); cat.getName(); => "Felix"
41. cat.setName("Felix"); cat.getName(); => "Felix" cat.setName("Mr. Meowsworthy"); cat.getName(); => ??
42. cat.setName("Felix"); cat.getName(); => "Felix" cat.setName("Mr. Meowsworthy"); cat.getName(); => "Mr. Meowsworthy"
43. String s = "Mr. Meowsworthy"; s.replaceAll("Mr", "Mrs"); s => ??
44. String s = "Mr. Meowsworthy"; s.replaceAll("Mr", "Mrs"); s => "Mr. Meowsworthy"
45. Inventing a class with its own interface to hold a piece of information is like inventing a new language to write every short story. This is anti- reuse, and, I think, results in an explosion of code in typical OO applications. Rich Hickey, creator of Clojure
46. Inventing a class with its own interface to hold a piece of information is like inventing a new language to write every short story. This is anti- reuse, and, I think, results in an explosion of code in typical OO applications. Rich Hickey, creator of Clojure
47. Inventing a class with its own interface to hold a piece of information is like inventing a new language to write every short story. This is anti- reuse, and, I think, results in an explosion of code in typical OO applications. Rich Hickey, creator of Clojure
48. com.sun.java.swing.plat.nimbus InternalFrameInternalFrameTitlePaneInternalFrameTitle PaneMaximizeButtonWindowNotFocusedState
49. InternalFrame InternalFrame Title Pane, InternalFrame Title Pane. Maximize Button Window, Not Focused State.
50. As you've noted, existing languages change slowly, if at all. Are we getting better languages? Many of the hot 'new' languages like Haskell and Erlang are in fact pretty old. Clojure builds on Lisp, which is really old. What is new is the willingness to utilize these languages in mainstream production environments. And that is a great thing, as we have largely maxed out the expressive capabilities of the C++/Java/C# languages, as evidenced by the prominence of XML and IDEs. Rich Hickey, creator of Clojure
51. As you've noted, existing languages change slowly, if at all. Are we getting better languages? Many of the hot 'new' languages like Haskell and Erlang are in fact pretty old. Clojure builds on Lisp, which is really old. What is new is the willingness to utilize these languages in mainstream production environments. And that is a great thing, as we have largely maxed out the expressive capabilities of the C++/Java/C# languages, as evidenced by the prominence of XML and IDEs. Rich Hickey, creator of Clojure