From 4c61a5bce3d39fb96bbfac620debbceeaa9f9f5f Mon Sep 17 00:00:00 2001
From: Chris
Date: Wed, 11 Mar 2015 16:03:58 -0400
Subject: [PATCH] added exercise
---
exercises/_assignment7.mdwn | 25 +++++++++++++++++++++++++
1 file changed, 25 insertions(+)
diff --git a/exercises/_assignment7.mdwn b/exercises/_assignment7.mdwn
index cd798ab0..d351b1b5 100644
--- a/exercises/_assignment7.mdwn
+++ b/exercises/_assignment7.mdwn
@@ -23,3 +23,28 @@ notes, prove that the evaluator does reduce expressions inside of
does not perform reductions in those positions.
+
+3. In the previous homework, one of the techniques for controlling
+evaluation order was wrapping expressions in a `let`: `let x = blah in
+foo`, you could be sure that `blah` would be evaluated by the time the
+interpreter considered `foo` (unless you did some fancy footwork with
+thunks). That suggests the following way to try to arrive at eager
+evaluation in our Haskell evaluator for CL:
+
+ reduce4 t = case t of
+ I -> I
+ K -> K
+ S -> S
+ FA a b ->
+ let b' = reduce4 b in
+ let a' = reduce4 a in
+ let t' = FA a' b' in
+ if (is_redex t') then reduce4 (reduce_one_step t')
+ else t'
+
+Will this work? That is, will `reduce4 (FA (FA K I) skomega)` go into
+an infinite loop? Run the code to find out, if you must, but write
+down your guess (and your rationale) first.
+
+
+
--
2.11.0