sum package:relude

Stricter version of sum.

>>> sum [1..10]
55

Monoid under addition.

Sum a <> Sum b = Sum (a + b)

Examples

>>> Sum 1 <> Sum 2 <> mempty
Sum {getSum = 3}

>>> mconcat [ Sum n | n <- [3 .. 9]]
Sum {getSum = 42}

Alternative version of asum that takes a function to map over.

>>> asumMap (\x -> if x > 2 then Just x else Nothing) [1..4]
Just 3

The sum of a collection of actions using (<|>), generalizing concat. asum is just like msum, but generalised to Alternative.

Examples

Basic usage:

>>> asum [Just "Hello", Nothing, Just "World"]
Just "Hello"

The sum of a collection of actions, generalizing biconcat.

Examples

Basic usage:

>>> biasum (Nothing, Nothing)
Nothing

>>> biasum (Nothing, Just 42)
Just 42

>>> biasum (Just 18, Nothing)
Just 18

>>> biasum (Just 18, Just 42)
Just 18