Sum package:ihaskell

Monoid under addition.

>>> getSum (Sum 1 <> Sum 2 <> mempty)
3

Sum :: a -> Sum a

sum :: (Foldable t, Num a) => t a -> a

The sum function computes the sum of the numbers of a structure.

Basic usage:

>>> sum []
0

>>> sum [42]
42

>>> sum [1..10]
55

>>> sum [4.1, 2.0, 1.7]
7.8

>>> sum [1..]
* Hangs forever *

An unboxed sum of the given reps

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

Basic usage, using the MonadPlus instance for Maybe:

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