Lists in Haskell

Accessing element in list through index:

[1, 2, 3] !! 2
--- 3

Head, tail, last

head [1, 2, 3]
--- 1

tail [1, 2, 3]
--- 2, 3

last [1, 2, 3]
--- 3

null, length

null [1, 2, 3]
--- False

null []
--- True

length [1, 2, 3]
--- 3

Range

[1, 2..10]
---[1,2,3,4,5,6,7,8,9,10]

[0.1, 0.2..1]
-- [0.1,0.2,0.30000000000000004,0.4,0.5,0.6,0.7000000000000001,0.8,0.9,1.0]

This works even with chars:

['A' .. 'Z']
--- "ABCDEFGHIJKLMNOPQRSTUVWXYZ"

elem

This function receives a value and a list and returns if the value is an element of the list.

1 `elem`[1, 2, 3]
--- True

cycle

With cycle, we can create a list that repeats its content for ever - we receive an infitite list. For example, [1, 2] would be turned into [1, 2, 1, 2, 1, 2 … and so on.

To cut the list which turns the infinite list cycle creates into an ending one:

take 10 (cycle[1, 2])
---[1,2,1,2,1,2,1,2,1,2]

The parameter “take” receives is the length of the list that should be generated.

repeat

It does what it suggests.

While generate an infitite list consisting only of 5’s:

repeat 5

To make it a fixed size: (10 times 5):

take 10 (repeat 5)