;; Declares a namespace which sets a unique name for your functions
;; Since Clojure runs on the JVM we have to
;; define a class
(ns clojure-tut.core
(:require [clojure.string :as str])
(:gen-class))
;; VARIABLES
;; Variables are immutable (value can't change) and they are
;; defined with def and start with letters or underscores
;; and can contain numbers also
(def randVar 10)
;; DATA TYPES
;; Types are assigned based on the value assigned
;; -9,223,372,036,854,775,808 to +9,223,372,036,854,775,807
(def aLong 15)
;; 4.94065645841246544e-324d to 1.79769313486231570e+308d
(def aDouble 1.23456)
;; A String
(def aString "Hello")
;; true or false
(def aBool true)
;; Get the data type
(type 15)
;; Check if no value (nil)
(nil? aLong)
;; Check if a value is positive
(pos? aLong)
;; Check if a number is negative
(neg? aLong)
;; Check if even
(even? aLong)
;; Check if odd
(odd? aLong)
;; Check if number
(number? aLong)
;; Check if integer
(integer? aLong)
;; Check if float
(float? aLong)
;; Check if zero
(zero? aLong)
;; FORMATTED OUTPUT
(format "This is a string %s" aString)
(format "5 spaces and %5d" aLong)
(format "Leading zeros %04d" aLong)
(format "%-4d left justified" aLong)
(format "3 decimals %.3f" aDouble)
;; STRINGS
(def str1 "This is my 2nd string")
;; Check if blank
(str/blank? str1)
;; Does string contain "my"
(str/includes? str1 "my")
;; Index of match
(str/index-of str1 "my")
;; Split string into vector using separator or Regex
(str/split str1 #" ")
(str/split str1 #"\d")
;; Join a collection into 1 string with a seperator
(str/join " " ["The" "Big" "Cheese"])
;; Replace all Regex with a string
;; There is also replace-first
(str/replace "I am 42" #"42" "43")
;; Remove whitespace at beginning and end
;; Also remove newlines with trim-newline
;; Remove left white space triml
;; and right trimr
(str/trim str1)
;; Uppercase
(str/upper-case str1)
;; Lowercase
(str/lower-case str1)
;; LISTS
;; Stores a list of values with multiple data types
(println (list "Dog" 1 3.4 true))
;; Get 1st Value
(println (first (list 1 2 3)))
;; Get rest of values
(println (rest (list 1 2 3)))
;; Get defined index
(println (nth (list 1 2 3) 1))
;; Add values to the right
(println (list* 1 2 [3 4]))
;; Add 1 value to the left
(println (cons 3 (list 1 2)))
;; SETS
;; List of unique values
(println (set '( 1 1 2)))
;; Get an index
(println (get (set '(3 2)) 2))
;; Append a value
(println (conj (set '(3 2)) 1))
;; Is value in set
(println (contains? (set '(3 2)) 3))
;; Remove value from set
(println (disj (set '(3 2)) 2))
;; VECTORS
(println (vector 1 "Dog"))
;; Get index
(println (get (vector 3 2) 1))
;; Append element
(println (conj (vector 1 2) 3))
;; Remove 1st item
(println (pop (vector 3 2)))
;; Return vector from one point to another
(println (subvec (vector 1 2 3 4) 1 3))
;; MAPS
;; Collection of key value pairs
(println (hash-map "Name" "Derek" "Age" 42))
;; Sorted lists sort based on keys
(println (sorted-map 3 42 2 "Banas" 1 "Derek"))
;; Return value mapped to key
(println (get (hash-map "Name" "Derek") "Name"))
;; Get value for the key
(println (find (hash-map "Name" "Derek" "Age" 42) "Name"))
;; Does map contain a key
(println (contains? (hash-map "Name" "Derek") "Age"))
;; Get list of keys
(println (keys (hash-map "Name" "Derek" "Age" 42)))
;; Get values
(println (vals (hash-map "Name" "Derek" "Age" 42)))
;; Merge maps
(println (merge-with + (hash-map "Name" "Derek") (hash-map "Age" 42)))
;; ATOMS
;; With atoms you can change a variables value
(defn atom-ex
[x]
;; Define the atoms value
(def atomEx (atom x))
;; Watchers can be attached to atoms and agents
;; to run functions when a value changes
(add-watch atomEx :watcher
(fn [key atom old-state new-state]
(println "atomEx changed from " old-state " to " new-state)))
;; Print the value
(println "1st x" @atomEx)
;; Change the value
(reset! atomEx 10)
(println "2nd x" @atomEx)
;; Change the value using a function
(swap! atomEx inc)
(println "Increment x" @atomEx)
)
;; AGENTS
;; Agents allow you to change values using functions
(defn agent-ex
[]
;; Create agent
(def tickets-sold (agent 0))
;; Add a value to an agent
(send tickets-sold + 15)
;; Added because there is a delay often
(println)
(println "Tickets " @tickets-sold)
;; Wait for the value to update with await-for
(send tickets-sold + 10)
(await-for 100 tickets-sold)
(println "Tickets " @tickets-sold)
;; Shutdown running agents
(shutdown-agents)
)
;; MATH
(println (+ 1 2 3)) ;; Add values together
(println(- 5 3 2)) ;; Subtract values
(println(* 2 5)) ;; Multiply Values
(println(/ 10 5)) ;; Divide Values
(println(mod 12 5)) ;; Modulus
(println(inc 5)) ;; Increment
(println(dec 5)) ;; Decrement
(println(Math/abs -10)) ;; Absolute Value
(println(Math/cbrt 8)) ;; Cube Root
(println(Math/sqrt 4)) ;; Square Root
(println(Math/ceil 4.5)) ;; Round up
(println(Math/floor 4.5)) ;; Round down
(println(Math/exp 1)) ;; e to the power of 1
(println(Math/hypot 2 2)) ;; sqrt(x^2 + y^2)
(println(Math/log 2.71828)) ;; Natural logarithm
(println(Math/log10 100)) ;; Base 10 log
(println(Math/max 1 5))
(println(Math/min 1 5))
(println(Math/pow 2 2)) ;; Power
;; Generate random number
(println (rand-int 20))
;; cos, sin, tan acos, asin, atan, cosh, sinh, tanh
;; Perform an operation on a collection
(reduce + [1 2 3])
(reduce - [1 2 3])
(Math/PI)
;; FUNCTIONS
;; Define a function with 1 parameter named name
(defn say-hello
"Receives a name and responds with Hello Again name"
;; Attributes for the function
[name]
;; Output the text and value
(println "Hello Again" name))
(defn get-sum
[x y]
;; The output from the last operation is returned
(+ x y))
;; You can receive an unknown number of parameters
(defn get-sum-more
([x y z]
(+ x y z))
([x y]
(+ x y)))
;; Receive a variable number of parameters in a list
(defn hello-you
[name]
;; Another way to combine strings
(str "Hello " name))
(defn hello-all
[& names]
;; Pass values to hello-you
(map hello-you names))
;; DECISION MAKING
;; RELATIONAL OPERATORS
;; = not= < <= > >=
(= 4 5)
(not= 4 5)
;; LOGICAL OPERATORS
;; and or not
(and true false)
(or true false)
(not true)
;; IF THEN ELSE
(defn can-vote
[age]
;; If the statement is true execute the 1st, or 2nd if false
(if (>= age 18)
(println "You can Vote")
(println "You can't Vote")))
(defn can-do-more
[age]
;; You can perform multiple actions with do
(if (>= age 18)
(do (println "You can Drive")
(println "You can Vote"))
(println "You can't Vote")))
;; WHEN
;; Is used when you want to do many things if true
(defn when-ex
[tof]
(when tof
(println "1st Thing")
(println "2nd Thing")))
;; COND
;; Check for multiple conditions
(defn what-grade
[n]
(cond
(< n 5) "Preschool"
(= n 5) "Kindergarten"
(and (> n 5) (<= n 18)) (format "Go to Grade %d" (- n 5))
:else "Go to College"))
;; LOOPING
;; WHILE LOOPS
;; Loop while condition is true
(defn one-to-x
[x]
;; Value that increments
(def i (atom 1))
;; Loop while true
(while (<= @i x)
(do
(println @i)
;; Increment value
(swap! i inc))))
;; DOTIMES LOOP
;; Execute a statement a set number of times
(defn dbl-to-x
[x]
;; i is incremented each time through
(dotimes [i x]
(println (* i 2))))
;; LOOP LOOP
;; Loop through values using recur to change a value
;; until a condition is no longer true
(defn triple-to-x
[x y]
;; Set starting value of i
(loop [i x]
;; Cycle while true
(when (< i y)
(println (* i 3))
;; Increment the value
(recur (+ i 1)))))
;; DOSEQ LOOP
;; Iterates through a sequence
(defn print-list
;; Holds list passed
[& nums]
;; As you cycle through the list store each item in x
(doseq [x nums]
(println x)))
;; FILE I/O
(use 'clojure.java.io)
(defn write-to-file
[file text]
;; with-open opens and closes the file
;; and then writes a string to a file
(with-open [wrtr (writer file)]
(.write wrtr text)))
(defn read-from-file
[file]
;; We can catch a potential file not found error
;; with exception handling
(try
;; Read from a file to a single string
(println (slurp file))
;; Catch the error and print it
(catch Exception e (println "Error : " (.getMessage e)))))
;; Append text to a file
(defn append-to-file
[file text]
(with-open [wrtr (writer file :append true)]
(.write wrtr text)))
;; Read 1 line at a time
(defn read-line-from-file
[file]
(with-open [rdr (reader file)]
(doseq [line (line-seq rdr)]
(println line))))
;; DESTRUCTURING
;; Binding of values in a data structure to symbols
(defn destruct
[]
(def vectVals [1 2 3 4])
;; Assign values to symbols
;; the-rest stores remaining values
(let [[one two & the-rest] vectVals]
(println one two the-rest)))
;; STRUCTMAPS
;; Used to define a complex custom type
(defn struct-map-ex
[]
;; Define a Struct
(defstruct Customer :Name :Phone)
;; Define a Struct Object
(def cust1 (struct Customer "Doug" 4125551212))
;; You can also assign to specific keys
(def cust2 (struct-map Customer :Name "Sally" :Phone 5551122))
(println cust1)
;; Access individual fields
(println (:Name cust2))
)
;; ADVANCED FUNCTIONS
;; Anonymous Functions
;; Function with no name
;; Create a list by multiplying all values by themselves
(map (fn [x] (* x x)) (range 1 10))
;; Compact anonymous function multiplies everything by 3
(map #(* % 3) (range 1 10))
;; Compact anon with 2 arguments
(#(* %1 %2) 2 3)
;; CLOJURES
;; Return a custom function
;; Run in Repl
;; (defn custom-multiplier
;; [mult-by]
;; #(* % mult-by))
;; (def mult-by-3 (custom-multiplier 3))
;; (mult-by-3 3)
;; Where your code starts execution
(defn -main
"I don't do a whole lot ... yet."
[& args]
;; FUNCTIONS
;; Call for the function to execute
(say-hello "Derek")
(get-sum 4 5)
(get-sum-more 1 2 3)
(hello-all "Doug" "Mary" "Paul")
(println "Mult by 3")
;; DECISION MAKING
(can-vote 17)
(can-do-more 24)
(when-ex true)
(what-grade 19)
;; ATOMS
(atom-ex 5)
;; LOOPING
(one-to-x 5)
(dbl-to-x 5)
(triple-to-x 1 5)
(print-list 7 8 9)
;; FILE I/O
(write-to-file "test.txt" "This is a sentence\n")
(read-from-file "test.txt")
(append-to-file "test.txt" "This is another sentence\n")
(read-line-from-file "test.txt")
;; DESTRUCTURING
(destruct)
;; STRUCTMAPS
(struct-map-ex)
;; AGENTS
(agent-ex)
;; TAKE DROP
(take-drop-ex)
)
(ns tut2.core
(:gen-class))
(defn take-drop
[]
;; FILTERING LISTS
;; TAKE DROP TAKE-WHILE DROP-WHILE FILTER
;; Remove 1st 2
(println (take 2 [1 2 3]))
;; Remove after the 1st
(println (drop 1 [1 2 3]))
;; Take what matches a condition
(println (take-while neg? [-1 0 1]))
;; Drop what matches a condition
(println (drop-while neg? [-1 0 1]))
;; Return what matches
(println (filter #(> % 2) [1 2 3 4]))
(println (rand) 0.5)
)
;; MACROS
;; Macros generate code when you need to define when
;; or if arguments should be evaluated
;; This macro will print different discounts based on
;; if the person is over 65 or not
(defmacro discount
([cond dis1 dis2]
;; Syntax Quoting tells clojure not to evaluate if, but
;; to just return it
(list `if cond dis1 dis2)))
;; Create (+ 2 5) when passed (2 + 5)
(defmacro reg-math
[calc]
(list (second calc) (first calc) (nth calc 2)))
;; Execute multiple statements with do
(defmacro do-more
[cond & body]
;; If condition is true combine and return all past
;; statements in a list for execution
(list `if cond (cons 'do body)))
(defmacro do-more-2
[cond & body]
;; You can surround everything with syntax quoting and
;; then unquote single values with ~ and multiples with
;; ~@
`(if ~cond (do ~@body)))
(defn -main
"I don't do a whole lot ... yet."
[& args]
(take-drop)
;; MACROS
(discount (> 25 65) (println "10% off") (println "Full Price"))
(reg-math (2 + 5))
;; macroexpand tells us what the macro does
(macroexpand `(reg-math (2 + 5)))
(do-more (< 1 2) (println "Hello") (println "Hello Again"))
(do-more-2 (< 1 2) (println "Hello") (println "Hello Again"))
)
