msum -package:invertible

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

Examples

Basic usage, using the MonadPlus instance for Maybe:

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

The sum of a collection of actions, generalizing concat. As of base 4.8.0.0, msum is just asum, specialized to MonadPlus.

The sum of a collection of actions, generalizing concat. msum is just like asum, but specialised to MonadPlus.

The sum of a collection of actions, generalizing concat

reduceWith getMonadSum

The sum of a collection of actions, generalizing concat. As of base 4.8.0.0, msum is just asum, specialized to MonadPlus.

The sum of a collection of actions, generalizing concatOf.

>>> msumOf both ("hello","world")
"helloworld"

>>> msumOf each (Nothing, Just "hello", Nothing)
Just "hello"

msum ≡ msumOf folded

msumOf :: MonadPlus m => Getter s (m a)     -> s -> m a
msumOf :: MonadPlus m => Fold s (m a)       -> s -> m a
msumOf :: MonadPlus m => Lens' s (m a)      -> s -> m a
msumOf :: MonadPlus m => Iso' s (m a)       -> s -> m a
msumOf :: MonadPlus m => Traversal' s (m a) -> s -> m a
msumOf :: MonadPlus m => Prism' s (m a)     -> s -> m a

The sum of a collection of actions.

>>> msumOf each ("hello","world")
"helloworld"

>>> msumOf each (Nothing, Just "hello", Nothing)
Just "hello"

msum ≡ msumOf folded

A description, or caption, for this media.

Alias for biasum.

A dual of lensProduct: a prism sum. The law

preview l (review l b) ≡ Just b

breaks with

>>> let badPrism :: Prism' (Maybe Char) (Either Char Char); badPrism = prismSum _Just _Just

>>> preview badPrism (review badPrism (Right 'x'))
Just (Left 'x')

We put in Right value, but get back Left. Are you looking for without?

An optional, string summary, intended to apply to all operations in this path.

Apply update functions to the terms and coefficients of a weighted sum.

This Haskell module exports various "from" functions for Either and Maybe.

sum

Sum norm.

Sum norm.

Extract a value from a SumType Example:

type Animal = SumType '[Owl, Cat, Toad]
let someAnimal = ... :: Animal

fromSumType (Proxy :: Proxy 0) someAnimal :: Maybe Owl
fromSumType (Proxy :: Proxy 1) someAnimal :: Maybe Cat
fromSumType (Proxy :: Proxy 2) someAnimal :: Maybe Toad

-- Compile-time error
-- fromSumType (Proxy :: Proxy 3) someAnimal