week9 tweak

[lambda.git] / week9.mdwn

diff --git a/week9.mdwn b/week9.mdwn
index 7028e89..568fc81 100644 (file)
--- a/week9.mdwn
+++ b/week9.mdwn
@@ -304,6 +304,15 @@ For expressions we already know how to interpret, `s'` will usually just be `s`.
                        eval expr2 ((c, value) :: g) s'
                ...
 
+Similarly:
+
+               ...
+               | Addition (expr1, expr2) ->
+                       let (value1, s') = eval expr1 g s
+                       in let (value2, s'') = eval expr2 g s'
+                       in (value1 + value2, s'')
+               ...
+
 Let's consider how to interpet our new syntactic forms `newref`, `deref`, and `setref`: