From 34fef03ba8ddcc9bdb2e07e402beddc6c715da5e Mon Sep 17 00:00:00 2001
From: "Elf M. Sternberg" <elf.sternberg@gmail.com>
Date: Tue, 28 Apr 2015 08:51:34 -0700
Subject: [PATCH] Caught a silly typo; now sufficient to support classic
 factorials with recursions.

---
 chap1.rkt | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/chap1.rkt b/chap1.rkt
index 5b0c323..f83041b 100644
--- a/chap1.rkt
+++ b/chap1.rkt
@@ -77,6 +77,8 @@
 (defprimitive car car 1)
 (defprimitive set-cdr! set-mcdr! 2)
 (defprimitive + + 2)
+(defprimitive - - 2)
+(defprimitive * * 2)
 (defpredicate lt < 2)
 (defpredicate eq? eq? 2)
 
@@ -135,7 +137,7 @@
 ; silly patch because of the mutatable lists
 
 (define-syntax mcaar (syntax-rules () ((_ e) (mcar (mcar e)))))
-(define-syntax mcadr (syntax-rules () ((_ e) (mcdr (mcar e)))))
+(define-syntax mcdar (syntax-rules () ((_ e) (mcdr (mcar e)))))
 
 ; Iterate through the environment, find an ID, return its associated
 ; value.
@@ -186,3 +188,5 @@
           (begin (display result) (toplevel))
           #f)))
   (toplevel))
+
+; (set! fact (lambda (x) (if (eq? x 0) 1 (* x (fact (- x 1))))))