From d3be9d07f791548dd8bb9b54d07e3b666cfa2379 Mon Sep 17 00:00:00 2001 From: jim Date: Mon, 23 Mar 2015 10:27:45 -0400 Subject: [PATCH 1/1] typo --- topics/week7_introducing_monads.mdwn | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/topics/week7_introducing_monads.mdwn b/topics/week7_introducing_monads.mdwn index 49993fff..7a7222e9 100644 --- a/topics/week7_introducing_monads.mdwn +++ b/topics/week7_introducing_monads.mdwn @@ -382,7 +382,7 @@ That can be helpful, but it only enables us to have _zero or one_ elements in th | [] -> [] | x' :: xs' -> List.append (k x') (catmap f xs') -Now we can have as many elements in the result for a given `α` as `k` cares to return. Another way to write `catmap k xs` is as (Haskell) `concat (map k cs)` or (OCaml) `List.flatten (List.map k xs)`. And this is just the definition of `mbind` or `>>=` for the List Monad. The definition of `mcomp` or `<=<`, that we gave above, differs only in that it's the way to compose two functions `j` and `k`, that you'd want to `catmap`, rather than the way to `catmap` one of those functions over a value that's already a list. +Now we can have as many elements in the result for a given `α` as `k` cares to return. Another way to write `catmap k xs` is as (Haskell) `concat (map k xs)` or (OCaml) `List.flatten (List.map k xs)`. And this is just the definition of `mbind` or `>>=` for the List Monad. The definition of `mcomp` or `<=<`, that we gave above, differs only in that it's the way to compose two functions `j` and `k`, that you'd want to `catmap`, rather than the way to `catmap` one of those functions over a value that's already a list. This example is a good intuitive basis for thinking about the notions of `mbind` and `mcomp` more generally. Thus `mbind` for the option/Maybe type takes an option value, applies `k` to its element (if there is one), and returns the resulting option value. `mbind` for a tree with `α`-labeled leaves would apply `k` to each of the leaves, and return a tree containing arbitrarily large subtrees in place of all its former leaves, depending on what `k` returned. -- 2.11.0