Data Structures

Clojure data structures are immutable meaning they can’t be changed in place like in many other programming languages.

Numbers

Clojure has all the basic number representation found in other programming languages plus its own Ratio type. Ratio represents a division of integers that can’t be reduced to an integer.

92
1.8
1/3

Strings

Strings can only be creted by using double quotes. Concatenation is done using the str function

1(str "Hello," " world!")

Maps

Map is a collection that maps keys to values. Clojure has two different map types a hashed and a sorted map.

1{:first-name "Duja"
2 :last-name "446"}

The function get is used to look up values. We can also treat the map as a function with the key as its argument to look up values

1(get {:a 0 :b 1} :a)
2; => 0
3
4({:a 0 :b 1} :b)
5; => 1

Keywords

Keywords are symbolic indentifiers that evalute to themselves. They can also be used as function that look up corresponding value in a data structure.

1{:a {:a 1 :b 2 :c 3}}
2; => 1

Vectors

Vectors are similar to arrays being indexed by contiguous integers.

1(get [3 2 1] 0)
2; => 3
3
4(get ["duja" 1 {:data "bbcc"}] 2)
5; => {:data "bbcc"}

The conj function is used to add element to the end of the vector.

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

Lists

Lists are similar to vectors beaing a linear list of values. However you can’t retrieve list values with get and conj puts the element at the front of the list.

1'(1 2 3 4)
2; => (1 2 3 4)
3
4(conj '(1 2 3) 4)
5; => (4 1 2 3)

Sets

Sets are like maps, the only difference being that sets hold only unique values.

1(hash-set 1 1 2 2)
2; => #{1 2}
3
4(:a #{:a 1 :b 2})
5; => 1
6
7(get #{:a 1 :b 2 :c 3} :c)
8; => 3