X-Git-Url: http://lambda.jimpryor.net/git/gitweb.cgi?p=lambda.git;a=blobdiff_plain;f=topics%2F_week7_monads.mdwn;h=3f2955e9f1fb6ebe476c4eee917a49d877652e1e;hp=fc6b41536b1f43cb94b5389fe114d41af5ca2f7d;hb=cb9c6590ec969e34555d9c9f56758c3e6c252ce5;hpb=7803c02633a9ff916c86b17f868161317be27bcc

diff --git a/topics/_week7_monads.mdwn b/topics/_week7_monads.mdwn
index fc6b4153..3f2955e9 100644
--- a/topics/_week7_monads.mdwn
+++ b/topics/_week7_monads.mdwn
@@ -48,5 +48,27 @@ We'll often write box types as a box containing the value of the free
 type variable.  So if our box type is `α List`, and `α == Int`, we
 would write
 
-<table border=2px>Int</table>
+<table border=2px><td>Int</td></table>
+
+for the type of a boxed Int.
+
+At the most general level, we'll talk about *Kleisli arrows*:
+
+P -> <table border=2px><td>Q</td></table>
+
+A Kleisli arrow is the type of a function from objects of type P to
+objects of type box Q, for some choice of type expressions P and Q.
+For instance, the following are arrows:
+
+Int -> <table border=2px><td>Bool</td></table>
+
+Int List -> <table border=2px><td>Int List</td></table>
+
+Note that the left-hand schema can itself be a boxed type.  That is,
+if `α List` is our box type, we can write the second arrow as
+
+<table border=2px><td>Int</td></table>
+->
+<table border=2px><td><table
+border=2px><td>Int</td></table></td></table>