This document provides an overview of Clojure concepts including recursion, sequence processing, pattern matching, protocols, macros, and more. It includes examples of: 1) Recursive functions for length and looping. 2) A balance function using recursion, pattern matching, and sequence processing to check balanced parentheses in a string. 3) Protocols and extending types to make objects moveable. 4) Defining macros to transform code, like replacing print statements.

1. CLOJURE WORKSHOP

2. RECURSION

3. (defn length
([collection]
(length collection 0))
([collection accumulator]
(if (empty? collection)
accumulator
(recur (rest collection) (inc accumulator)))))

4. (loop [x 10]
(when (> x 1)
(println x)
(recur (- x 2))))

5. SEQUENCE PROCESSING

6. RECURSIVE
(defn
balance
([string]
(balance
0
(seq
string)))
([count
[head
&
tail
:as
chars]]
(if
(not
(empty?
chars))
(case
head
(
(recur
(inc
count)
tail)
)
(if
(zero?
count)
false
(recur
(dec
count)
tail))
(recur
count
tail))
true)))

7. PATTERN MATCHING
(defn-­‐match
balance
([?string]
(balance
0
(seq
string)))
([_
[]
]
true)
([?count
[(
&
?tail]]
(balance
(inc
count)
tail))
([0
[)
&
_]
]
false)
([?count
[)
&
?tail]]
(balance
(dec
count)
tail))
([?count
[_
&
?tail]]
(balance
count
tail)))

8. SEQUENCE PROCESSING
(defn
balance
[string]
(-­‐>>
string
seq
(map
{(
inc
)
dec})
(filter
identity)
(reductions
#(%2
%1)
0)
(filter
neg?)
empty?))

9. PROTOCOLS

10. (defrecord
CartesianCoordinate
[x
y])

11. (defrecord
PolarCoordinate
[distance
angle])

12. (defprotocol
Moveable
(move-­‐north
[self
amount])
(move-­‐east
[self
amount]))

13. (extend-­‐type
CartesianCoordinate
Moveable
(move-­‐north
[{x
:x
y
:y}
ammount]
(CartesianCoordinate.
(+
x
ammount)
y))
(move-­‐east
[{x
:x
y
:y}
ammount]
(CartesianCoordinate.
x
(+
y
ammount))))

14. (defrecord
CenterPointRectangle
[center-­‐point
width
height])

15. (defrecord
CornerPointRectangle
[top-­‐left
bottom-­‐right])

16. (extend-­‐type
CenterPointRectangle
Moveable
(move-­‐north
[self
ammount]
(update-­‐in
self
[:center-­‐point]
#(move-­‐x
%
ammount)))
(move-­‐east
[self
ammount]
(update-­‐in
self
[:center-­‐point]
#(move-­‐y
%
ammount))))

17. MACROS

18. '(println "Hello, World")

19. '(println "Hello, World")
=> (println "Hello, World")

20. (first '(println "Hello, World"))

21. (first '(println "Hello, World"))
=> println

22. (def function-name
(first '(println "Hello, World")))
(list function-name "Goodbye, Cruel World")

23. (def function-name
(first '(println "Hello, World")))
(list function-name "Goodbye, Cruel World")
=> (println "Goodbye, Cruel World")

24. (def function-name
(first '(println "Hello, World")))
(def new-code
(list function-name "Goodbye, Cruel World"))
(eval new-code)

25. (def function-name
(first '(println "Hello, World")))
(def new-code
(list function-name "Goodbye, Cruel World"))
(eval new-code)
prints: “Goodbye, Cruel World”

26. (defmacro emoify [original-code]
(let [function-name (first '(println "Hello, World"))]
(list function-name "Goodbye, Cruel World")
(emoify (println "Hello, World"))

27. (defmacro emoify [original-code]
(let [function-name (first '(println "Hello, World"))]
(list function-name "Goodbye, Cruel World")
(emoify (println "Hello, World"))
prints: “Goodbye, Cruel World”

28. FIN
Questions?