# !/usr/local/bin/kermit + ; From: "Nguyen, Dat" ; To: "'Frank da Cruz'" ; Subject: A Faster Towers of Hanoi Script ; Date: Tue, 15 Jan 2002 10:00:48 -0600 ; ; You are very thorough in verifying input parameters, sometimes at the ; expense of the execution of recursive macro. I reworked the Tower_Of_Hanoi ; script to separate the verification of the inputs and the execution of the ; recursive computation. I think this pattern is applicable to similar ; recursive macros. ; ; h a n o i -- Towers Of Hanoi ; ; Author: Dat Thuc Nguyen, 21 Sep 2001 ; Revised 15 Jan 2002 ; ; \%1 Number_of_Discs ; \%2 Start_Peg ; \%3 Goal_Peg define Tower_Of_Hanoi { if < \v(argc) 4 exit 1 Usage: hanoi ndisks startpeg goalpeg if not numeric \%1 exit 1 \%1: not a number if not numeric \%2 exit 1 \%2: not a number if not numeric \%3 exit 1 \%3: not a number if ( < \%1 1 || < \%2 1 || < \%3 1 ) exit 1 Numbers must be positive if ( > \%2 3 || > \%3 3 ) exit 1 Peg must be 1 or 2 or 3 if ( = \%2 \%3 ) exit 1 Peg numbers must be distinct local recursive define recursive { if = 1 \%1 { echo Move Top Disc from peg \%2 to peg \%3. } else { (recursive (- \%1 1) \%2 (- 6 (+ \%2 \%3))) recursive 1 \%2 \%3 (recursive (- \%1 1) (- 6 (+ \%2 \%3)) \%3) } } recursive \%1 \%2 \%3 exit 0 }