mapM_

Map each element of a structure to a monadic action, evaluate these actions from left to right, and ignore the results. For a version that doesn't ignore the results see mapM. mapM_ is just like traverse_, but specialised to monadic actions.

Apply the action to all values in the stream. Note: if you want to pass the values instead of consuming them, use iterM instead. Subject to fusion

Apply the action to all values in the stream. Subject to fusion Since 0.3.0

Perform a computation on each Word8 in a stream. Since 1.0.10

Consume all values using a monadic function

Converts an effectful function to a fold. Specialized version of sink.

Maps a side effect over an InputStream. mapM_ f s produces a new input stream that passes all output from s through the side-effecting IO action f. Example:

ghci> Streams.fromList [1,2,3] >>=
Streams.mapM_ (putStrLn . show . (*2)) >>=
Streams.toList
2
4
6
[1,2,3]

A side-effecting map over the key-value records of a hash table. O(n).

See the documentation for this function in mapM_.

See the documentation for this function in mapM_.

See the documentation for this function in mapM_.

See the documentation for this function in Data.HashTable.Class#v:mapM_.

Reduce a stream to its return value with a monadic action.

>>> S.mapM_ Prelude.print $ each [1..3]
1
2
3

>>> rest <- S.mapM_ Prelude.print $ S.splitAt 3 $ each [1..10]
1
2
3

>>> S.sum rest
49 :> ()

Map each element of a structure to a monadic action, evaluate these actions from left to right, and ignore the results. For a version that doesn't ignore the results see mapM. As of base 4.8.0.0, mapM_ is just traverse_, specialized to Monad.

O(n) Apply the monadic action to all elements of a vector and ignore the results

O(n) Apply the monadic action to all elements of a vector and ignore the results

O(n) Apply the monadic action to all elements of a vector and ignore the results

O(n) Apply the monadic action to all elements of a vector and ignore the results

Synonym for omapM_

A map in monad space, discarding results.

mapM_ = Stream.drain . Stream.mapM

Apply a monadic action to each element of the stream and discard the output of the action. This is not really a pure transformation operation but a transformation followed by fold.

A mapM_ equivalent.

Map each element of a structure to a monadic action, evaluate these actions from left to right, and ignore the results. For a version that doesn't ignore the results see mapM. mapM_ = traverse_