Functions

Conditional Expressions

abs :: Int -> Int
abs n = if n >= 0 then n else -n

Can be nested

signum :: Int -> Int
signum n = if n < 0 then -1 else
            if n == 0 then 0 else 1

Conditional expressions must always have an else branch, which avoids any possible ....... # 1

Alternative is guarded equations

abs n | n >= 0  = n
            | otherwise = n

| means such that

Clear definition

not :: Bool -> Bool
not False = True
not True = False

Symbol _ is a while card that matches any argument values.

Patterns are matched in order.

_ && _ = False
True && True = True

Any 2 arguments would satisfy the first one, so True would never be outputted Patterns may not repeat variables.

Internally, every non-empty list is constructed by repeated use of an (:) called 'cons' that adds an element to the start of a list
Functions on lists can be defined used x:xs patterns
x:xs patterns only match non-empty lists
Patterns must be parenthesised, because application has priority over (:)

Constructed without naming the functions by using lambda expressions. Nameless function that takes a number x and returns the result x+x

Typed as \.

Used to give a formal mean to functions defined using currying Can be used to avoid naming functions that are only referenced once,

An operator written between its two arguments can be converted into a curried function written before its two arguments by using parentheses.