* package:ihaskell

Low word of signed integer multiply.

Exponentiation.

Sequence actions, discarding the value of the first argument.

Examples

If used in conjunction with the Applicative instance for Maybe, you can chain Maybe computations, with a possible "early return" in case of Nothing.

>>> Just 2 *> Just 3
Just 3

>>> Nothing *> Just 3
Nothing

Of course a more interesting use case would be to have effectful computations instead of just returning pure values.

>>> import Data.Char

>>> import Text.ParserCombinators.ReadP

>>> let p = string "my name is " *> munch1 isAlpha <* eof

>>> readP_to_S p "my name is Simon"
[("Simon","")]

Sequence actions, discarding the value of the second argument.

A variant of <*> with the arguments reversed.

Sequential application. A few functors support an implementation of <*> that is more efficient than the default one.

Example

Used in combination with (<$>), (<*>) can be used to build a record.

>>> data MyState = MyState {arg1 :: Foo, arg2 :: Bar, arg3 :: Baz}

>>> produceFoo :: Applicative f => f Foo

>>> produceBar :: Applicative f => f Bar

>>> produceBaz :: Applicative f => f Baz

>>> mkState :: Applicative f => f MyState

>>> mkState = MyState <$> produceFoo <*> produceBar <*> produceBaz