In Haskell, lists are defined as a homogeneous data structure that stores elements of the same type. They can be constructed using the ‘:‘ operator (cons) and the empty list ‘[]‘. Lists are recursive, and each element is linked to the next using the cons operator.
Here’s an example list of integers:
intList :: [Int]
intList = 1 : 2 : 3 : 4 : 5 : []Let’s examine the Haskell list more in-depth in LaTeX format.
A list of elements of type ‘a‘ can be represented as ‘[a]‘. The type signature of the cons operator ‘:‘ is:
(:) :: a -> [a] -> [a]This means that the cons operator ‘:‘ takes an element of type ‘a‘ and a list of elements of type ‘[a]‘, and then returns a new list of elements of type ‘[a]‘.
Given the list of integers ‘intList‘ from above, we can represent the construction of the list in LaTeX:
intList = 1 : (2 : (3 : (4 : (5 : []))))
In Haskell, you can also define lists using the literal syntax, which is more concise:
intList :: [Int]
intList = [1, 2, 3, 4, 5]Here is a chart visualizing how ‘intList‘ is represented as a linked list:
In this chart, indices are the positions of each element in the list, values are the elements of the list, the colons ‘:‘ represent the cons operator, and the empty brackets ‘[]‘ denote the end of the list.