15 lines
388 B
Markdown
15 lines
388 B
Markdown
Example: List
|
||
-------------
|
||
|
||
- `[] :: * -> *` an <span class="yellow">Endofunctor</span>
|
||
- \\(⊙:M×M→M\\) a nat. trans. (`join :: M (M a) -> M a`)
|
||
- \\(η:I→M\\) a nat. trans.
|
||
|
||
<pre class="haskell"><code>-- In Haskell ⊙ is "join" in "Control.Monad"
|
||
join :: [[a]] -> [a]
|
||
join = concat
|
||
|
||
-- In Haskell the "return" function (unfortunate name)
|
||
η :: a -> [a]
|
||
η x = [x]</code></pre>
|