Methods
(static) mapM(f, m) → {Object}
Map each element of a structure to a monadic action, evaluate these actions from left to right,
and collect the results. This function is essentially the same as traverse but restricted to
monads.
Haskell> mapM :: Monad m => (a -> m b) -> t a -> m (t b)
Parameters:
| Name | Type | Description |
|---|---|---|
f |
function | The function to map |
m |
Object | The monad to traverse |
- Source:
Returns:
A collection of the results of the traversal
- Type
- Object
Example
const mb = just(1);
const lst = list(1,2,3);
const f = x => list(x + 7);
mapM(f, mb); // => [Just [8:[]]:[]]
mapM(f, lst); // => [[8:9:10:[]]:[[]]:[]](static) sequence(m) → {Object}
Evaluate each monadic action in a structure from left to right, and collect the results.
Haskell> sequence :: Monad m => t (m a) -> m (t a)
Parameters:
| Name | Type | Description |
|---|---|---|
m |
Object | The monadic collection of actions |
- Source:
Returns:
A collection of the results
- Type
- Object
Example
const mb = just(1);
const mmb = just(mb);
const lst = list(1,2,3);
const llst = list(lst);
sequence(mmb); // => Just Just 1
sequence(llst); // => [[1:[]]:[2:[]]:[3:[]]:[]](static) Traversable() → {boolean}
A Traversable is a functor representing data structures that can be walked over or "traversed"
from left to right (useful in trees, for example). They must define a traverse method and also
be instances of Functor and Foldable.
Parameters:
| Type | Description |
|---|---|
| * | Any object |
- Source:
Returns:
true if an object is an instance of Traversable and false otherwise
- Type
- boolean
(static) traverse(f, a) → {Object}
Map each element of a structure to an action, evaluate these actions from left to right, and
collect the results.
Haskell> traverse :: Applicative f => (a -> f b) -> t a -> f (t b)
Parameters:
| Name | Type | Description |
|---|---|---|
f |
function | The function to map |
a |
Object | The traversable structure to traverse |
- Source:
Returns:
A collection of the results of the traversal
- Type
- Object
Example
const mb = just(1);
const tup = tuple(1,2);
const lst = list(1,2,3);
const f = x => list(x + 7);
traverse(f, mb); // => [Just 8:[]]
traverse(f, tup); // => [(1,9):[]]
traverse(f)(lst); // => [[8:9:10:[]]:[]]