X-Git-Url: http://lambda.jimpryor.net/git/gitweb.cgi?p=lambda.git;a=blobdiff_plain;f=manipulating_trees_with_monads.mdwn;h=6677479111598f3801575d62eb278f4afa1da602;hp=59d44584dbcb1331d816bda15f744a2c4f449626;hb=06846722f1be7c898c2c2b1c33ac2b35955553b7;hpb=ef7c19f2fa5f5db94a38408896a952a56402ce98 diff --git a/manipulating_trees_with_monads.mdwn b/manipulating_trees_with_monads.mdwn index 59d44584..66774791 100644 --- a/manipulating_trees_with_monads.mdwn +++ b/manipulating_trees_with_monads.mdwn @@ -133,8 +133,8 @@ of that function. It would be a simple matter to turn an *integer* into an `int reader`: - let int_getter : int -> int reader = fun (a : int) -> fun (modifier : int -> int) -> modifier a;; - int_getter 2 (fun i -> i + i);; + let asker : int -> int reader = fun (a : int) -> fun (modifier : int -> int) -> modifier a;; + asker 2 (fun i -> i + i);; - : int = 4 But how do we do the analagous transformation when our `int`s are scattered over the leaves of a tree? How do we turn an `int tree` into a reader? @@ -185,17 +185,17 @@ Then we can expect that supplying it to our `int tree reader` will double all th In more fanciful terms, the `tree_monadize` function builds plumbing that connects all of the leaves of a tree into one connected monadic network; it threads the `'b reader` monad through the original tree's leaves. - # tree_monadize t1 int_getter double;; + # tree_monadize t1 asker double;; - : int tree = Node (Node (Leaf 4, Leaf 6), Node (Leaf 10, Node (Leaf 14, Leaf 22))) Here, our environment is the doubling function (`fun i -> i + i`). If we apply the very same `int tree reader` (namely, `tree_monadize -t1 int_getter`) to a different `int -> int` function---say, the +t1 asker`) to a different `int -> int` function---say, the squaring function, `fun i -> i * i`---we get an entirely different result: - # tree_monadize t1 int_getter square;; + # tree_monadize t1 asker square;; - : int tree = Node (Node (Leaf 4, Leaf 9), Node (Leaf 25, Node (Leaf 49, Leaf 121)))