Getting started with Clojure - Part 2

In this section, the main focus is on the different data types supported by Clojure. We also learn how to create and call functions.

Source : https://www.codeschool.com/code_tv/getting-started-with-clojure-part-2

• 4. Literal Data Types
• Built-in syntax for many data types
• Strings - e.g "hello world", can have line breaks
• Regular Expressions - e.g #"foo", java regular expressions
• Numbers - Long (123), Hex (0x11), Floating point(123.24), Other bases (8r1234 for radix 8), Big Integer (1232131N), Big Decimal (231313.1232M), Ratios (11/3) 
• Symbols/Keywords - 
• symbols - foo (normal symbol) , bar/foo (symbol with a namespace) 
• keywords - :foo (normal keyword) , com.test/foo (keyword with a namespace)
• Vectors/Lists/Maps/Sets
• Vector - sequence of values accessed by an index. similar to arrays. heterogenous (true to all 'collection' data types) 
• [1 "two" [3.0 "four"]]
• List - (1 "two" [3.0 "four"])
• Map - dictionary type. has keys and values in pairs. use line break for readability. 
• {"name" "RR" "age" 30}
• {:name "RR" :birthday [01 01] [12 34] 97}
• Set - #{1 2 3 "four"}
• 5. Evaluation
• Most things in Clojure evaluate to themselves - Numbers, String, Keywords, Maps/vectors/sets
• Some things don't - Lists/Symbols
• List evaluates to an invocation
• First item is an operation, rest are arguments
• evaluation is applied recursively 
• e.g (+ 1 2 4),  (println "hello")
• Defining functions
• defined with "fn" operator 
• arguments are listed in a vector
• value of the last expression is the function return val 
• e.g (fn [x y] (println x y) (+ x y))
• to invoke the above ((fn [x y] (println x y) (+ x y)) 4 5) - the highlighted section being the function and the rest being arguments
• 6. Naming things 
• Use "def" operator to create a var
• Vars associate symbols with values
• Value of a symbol is the value of a var
• e.g (def foo 3), (def bar [1 2 {:a 12}]
• Naming a function
• for the above function, (def add_nos (fn [x y] (println x y) (+ x y)))
• to call the above (add_nos 4 5)
• Easier way of naming a function 
•  (defn add_nos [x y] (println x y) (+ x y))
• the same var is defined for both -> #'user/add_nos