Courses/CS 460/Fall 2005/Homework/Josh Cain/Oct 22

From CSWiki

Arbor Day

local
   Trees = [ash cedar maple sycamore]
   Surnames = [becker clary delgado erichsen]
   FirstNames = [george harvey ivan john]
   % If Zs is not instantiated (or at least not bounded), then 
   % Xs and Ys should be. Otherwise the number of solutions will grow 
   % without limit.    
   proc {Append ?Xs ?Ys ?Zs}
      choice
         Xs = nil
 	 Ys = Zs
      [] Head XRest ZRest in
	 Xs = Head|XRest 
	 Zs = Head|ZRest
	 {Append XRest Ys ZRest}
      end
   end   
   % Value is the value of field Property in the record MPs
   % Both Property and Value may be uninstantiated
   proc {IsAPropertyValue MPs ?Property ?Value}
      {IsAMember Property#Value {Record.toListInd MPs}}
   end
   proc {IsATree ?Tree} {IsAMember Tree Trees} end
   proc {IsASurname ?Surnames} {IsAMember Surname Surnames} end
   proc {IsAFirstName ?FirstName} {IsAMember FirstName FirstName} end
   proc {IsAMember ?X Xs} {Append _ X|_ Xs} end
   proc {IsATail ?Xs ?Tail} {Append _ Tail Xs} end
   proc {Clue1 MPs}
      Surname
   in
      % George is not surnamed Mr. Clary or Mr. Becker
      {IsAPropertyValue MPs Surname george}
      {IsASurname Surname}
      Surname == clary = false
      Surname == becker = false
   end
   proc {Clue2 MPs}
      FirstName
      Tree
   in
      % Mr. Clary
      {IsAPropertyValue MPs clary FirstName}
      {IsAFirstName FirstName}
      % planted neither the cedar tree nor the maple tree
      {IsAPropertyValue MPs Tree FirstName}
      {IsATree Tree}
      Tree == cedar = false
      Tree == maple = false
   end
   proc {Clue3 MPs}
      Surname
   in
      % Harvey is not surnamed Clary
      {IsAPropertyValue MPs Surname harvey}
      {IsASurname Surname}
      Surname == clary = false
   end   
   proc {Clue4 MPs}
      FirstName
   in
      % Neither John nor Ivan planted the ash tree
      {IsAPropertyValue MPs ash FirstName}
      {IsAFirstName FirstName}
      FirstName == john = false
      FirstName == ivan = false
   end 
   proc {Clue5 MPs}
      Tree Surname
   in
      % George did not plant the maple tree
      {IsAPropertyValue MPs Tree george}
      {IsATree Tree}
      Tree == maple = false
      % George is not surnamed Delgado
      {IsAPropertyValue MPs Surname george}
      {IsASurname Surname}
      Surname == delgado = false
   end
   proc {Clue6 MPs}
      Tree
   in
      %Mr. Erichsen did not plant the ash tree
      {IsAPropertyValue MPs Tree erichsen}
      Tree == ash = false
   end
   proc {Clue7 MPs}
      Tree Surname
   in
      % John did not plant the maple tree
      {IsAPropertyValue MPs Tree john}
      {IsATree Tree}
      Tree == sycamore = false
      % George is not surnamed Becker
      {IsAPropertyValue MPs Surname john}
      {IsASurname Surname}
      Surname == becker = false
   end   
   fun {ArborDay}
      Properties = {FoldR [Trees Surnames] Append nil}
      MPs = {MakeRecord menProperties Properties}
   in
      {Clue1 MPs}
      {Clue2 MPs}
      {Clue3 MPs}
      {Clue4 MPs}
      {Clue5 MPs}
      {Clue6 MPs}
      {Clue7 MPs}
      MPs
   end
in
   {Browse {SearchAll ArborDay}}
end