From a967a60994565faa7a8537bfad55bb6f7b209f3c Mon Sep 17 00:00:00 2001
From: Felix Martin <mail@felixm.de>
Date: Tue, 2 Mar 2021 16:55:36 -0500
Subject: [PATCH] Implement till 4.63

---
 ex-4_61-xx.scm      | 42 +++++++++++++++++++++++++++++++++++++++---
 misc/sicp-query.scm | 12 ++++++++++++
 2 files changed, 51 insertions(+), 3 deletions(-)

diff --git a/ex-4_61-xx.scm b/ex-4_61-xx.scm
index b426f44..898844f 100644
--- a/ex-4_61-xx.scm
+++ b/ex-4_61-xx.scm
@@ -33,8 +33,44 @@
 
 (display "\nex-4.62 - last-pair\n")
 
-(display "\nex-4.63\n")
+(eval-query '(rule (last-pair (?x . ()) (?x . ()))))
+(eval-query
+  '(rule (last-pair (?u . ?v) ?x)
+         (last-pair ?v ?x)))
 
-;(display "\nex-4.64\n")
-;(display "\nex-4.65\n")
+(eval-query '(last-pair (1 2 3) ?y))
+(eval-query '(last-pair (3) ?y))
+(eval-query '(last-pair (2 3 4 5 ?x) (3)))
+(newline)
+
+; (eval-query '(last-pair ?x (3))) results in an endless loop because there is
+; no definite answer. Any arbitrary number of symbols before the 3 would form a
+; solution.
+
+(display "\nex-4.63 - genesis-family\n")
+
+; Formulate rules such as ``If S is the son of F, and F is the son of G, then S
+; is the grandson of G'' and ``If W is the wife of M, and S is the son of W,
+; then S is the son of M'' (which was supposedly more true in biblical times
+; than today) that will enable the query system to find the grandson of Cain;
+; the sons of Lamech; the grandsons of Methushael. (See exercise 4.69 for some
+; rules to deduce more complicated relationships.)
+
+(eval-query '(rule (grandson ?grandparent ?grandson)
+                   (and (nson ?grandparent ?son)
+                        (nson ?son ?grandson))))
+
+(eval-query '(rule (nson ?parent ?son)
+                   (or (son ?parent ?son)
+                       (and (wife ?parent ?wife)
+                            (son ?wife ?son)))))
+
+(eval-query '(grandson Cain ?x))
+(eval-query '(nson Lamech ?x))
+(eval-query '(grandson Methushael ?x))
+(newline)
+
+(display "\nex-4.64\n")
+
+(display "\nex-4.65\n")
 
diff --git a/misc/sicp-query.scm b/misc/sicp-query.scm
index 43b31aa..e537d24 100644
--- a/misc/sicp-query.scm
+++ b/misc/sicp-query.scm
@@ -665,6 +665,18 @@
       (or (supervisor ?staff-person ?boss)
           (and (supervisor ?staff-person ?middle-manager)
                (outranked-by ?middle-manager ?boss))))
+
+; From 4.63
+(son Adam Cain)
+(son Cain Enoch)
+(son Enoch Irad)
+(son Irad Mehujael)
+(son Mehujael Methushael)
+(son Methushael Lamech)
+(wife Lamech Ada)
+(son Ada Jabal)
+(son Ada Jubal)
+
 ))
 
 ;; felixm: for easier use from MIT-Scheme