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author
Chris Barker
<barker@omega.(none)>
Sat, 27 Nov 2010 04:49:06 +0000
(23:49 -0500)
committer
Chris Barker
<barker@omega.(none)>
Sat, 27 Nov 2010 04:49:06 +0000
(23:49 -0500)
zipper-lists-continuations.mdwn
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diff --git
a/zipper-lists-continuations.mdwn
b/zipper-lists-continuations.mdwn
index
bfd144c
..
6ec4d34
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(file)
--- a/
zipper-lists-continuations.mdwn
+++ b/
zipper-lists-continuations.mdwn
@@
-26,10
+26,10
@@
constructor is
then we can deduce the unit and the bind:
then we can deduce the unit and the bind:
- runit x:'a -> 'a reader = fun (e:env) -> x
+ r
_
unit x:'a -> 'a reader = fun (e:env) -> x
Since the type of an `'a reader` is `fun e:env -> 'a` (by definition),
Since the type of an `'a reader` is `fun e:env -> 'a` (by definition),
-the type of the `runit` function is `'a -> e:env -> 'a`, which is a
+the type of the `r
_
unit` function is `'a -> e:env -> 'a`, which is a
specific case of the type of the *K* combinator. So it makes sense
that *K* is the unit for the reader monad.
specific case of the type of the *K* combinator. So it makes sense
that *K* is the unit for the reader monad.
@@
-43,7
+43,8
@@
We can deduce the correct `bind` function as follows:
We have to open up the `u` box and get out the `'a` object in order to
feed it to `f`. Since `u` is a function from environments to
We have to open up the `u` box and get out the `'a` object in order to
feed it to `f`. Since `u` is a function from environments to
-objects of type `'a`, we'll have
+objects of type `'a`, the way we open a box in this monad is
+by applying it to an environment:
.... f (u e) ...
.... f (u e) ...