Lists

Definition 251.1(Lists).

Homogeneous collection of elements. Indexing starts at 0.

Infix list operators

• Lists are concatenated by the ++ operator. Haskell has to iterate through the entire list on the left.
• Elements can be prepended to lists in O(1) time by using the : operator 'A':" SMALL CAT"
• Indices are accessed using the !! operator [9.4,33.2,96.2,11.2,23.25] !! 1
• Relational operators compare lists in lexicographical order. Lists of different sizes can be compared.

Prefix list operations

• length
• null checks if a list is empty.
• reverse
• take takes a number and a list, and extracts said number of elements from the beginning of the list.
• drop opposite of take
• maximum works on all lists which can be ordered
• minimum ditto
• sum
• elem takes a thing and a list of things; returns true if thing is in list.
• cycle takes a list and cycles it into an infinite list.
• repeat takes an element and produces an infinite list of just that element.

Do not use these on empty lists!

• head returns the first element
• tail pops the first element and returns the remnant (‘tail’)
• last returns the last element
• init pops the last element and returns the remnant