Animals example (animals.sc2).
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In this script file some of the interactive features of Progol
are demonstrated. Progol contains a Prolog interpreter which
sticks closely to Edinburgh syntax. The interpreter is capable
of running Prolog programs containing cuts, and
calls to some standard Prolog system predicates including
is/2, =</2, arg/3, var/1, read/1, and write/1. Comments
between `======' lines are insterspersed between Progol input an output
below.

Try starting Progol as follows.
======
scye.comlab_{{26}}? progol
CProgol Version 4.1

|- help?
The following system predicates are available:
  !               , /2            -> /2           ; /2            
  < /2            = /2            =.. /2          =< /2           
  == /2           > /2            >= /2           @< /2           
  @=< /2          @> /2           @>= /2          \+ /1           
  \= /2           \== /2          advise/1        any/1           
  arg/3           asserta/1       bagof/3         clause/2        
  clause/3        commutative/1   commutatives    constant/1      
  consult/1       determination/2 element/2       float/1         
  functor/3       generalise/1    help            help/1          
  int/1           is/2            length/2        listing         
  listing/1       modeb/2         modeh/2         modes           
  name/2          nat/1           nl              noreductive     
  nosplit         nospy           not/1           notrace         
  number/1        op/3            ops             otherwise       
  parity          read/1          reconsult/1     record/2        
  reduce/1        reductive       repeat          retract/1       
  retract/2       see/1           seen            set/2           
  setof/3         settings        sort/2          spies           
  split           spy/1           stats           tab/1           
  tell/1          test/1          told            trace           
  true            var/1           write/1         
Help for system predicates using help(Predicate/Arity)
yes
[:- help? - Time taken 0.03s]

======
The query `help?' gives a list of all system predicates defined.

Brief help on any particular command can be got by typing help(Command/Arity)
for a particular command with given arity. For instance help
on the command reconsult/1 can be got as follows.
======

|- help(reconsult/1)?
[reconsult/1 - reconsults file]
yes
[:- help(reconsult/1)? - Time taken 0.00s]

======
Note that, as with Clocksin and Mellish Prolog, a list of files can be
reconsulted using the notation [file1,file2,..]
Below the animals.pl file is reconsulted.
======

|- [animals]?
[:- set(c,3)? - Time taken 0.00s]
[:- modeh(1,class(+animal,#class))? - Time taken 0.00s]
[:- modeb(1,has_milk(+animal))? - Time taken 0.00s]
[:- modeb(1,has_gills(+animal))? - Time taken 0.00s]
[:- modeb(1,has_covering(+animal,#covering))? - Time taken 0.00s]
[:- modeb(1,has_legs(+animal,#nat))? - Time taken 0.00s]
[:- modeb(1,homeothermic(+animal))? - Time taken 0.00s]
[:- modeb(1,has_eggs(+animal))? - Time taken 0.00s]
[:- modeb(100,habitat(+animal,#habitat))? - Time taken 0.00s]
[:- modeh(1,false)? - Time taken 0.00s]
[:- modeb(1,class(+animal,#class))? - Time taken 0.00s]
yes
[:- [animals]? - Time taken 0.15s]

======
A listing of the user-defined predicate class/2 can be produced
as follows.
======

|- listing(class/2)?
class(dog,mammal).
class(dolphin,mammal).
class(platypus,mammal).
class(bat,mammal).
class(trout,fish).
class(herring,fish).
class(shark,fish).
class(eel,fish).
class(lizard,reptile).
class(crocodile,reptile).
class(t_rex,reptile).
class(snake,reptile).
class(turtle,reptile).
class(eagle,bird).
class(ostrich,bird).
class(penguin,bird).
[Total number of clauses = 16]
yes
[:- listing(class/2)? - Time taken 0.02s]

======
Generalisation of the predicate class/2 is carried out below.
======

|- generalise(class/2)?
[Generalising class(dog,mammal).]
[Most specific clause is]
class(A,mammal) :- has_milk(A), has_covering(A,hair), has_legs(A,
	4), homeothermic(A), habitat(A,land).
[C:-6,4,10,0 class(A,mammal).]
[C:3,4,0,0 class(A,mammal) :- has_milk(A).]
[2 explored search nodes]
[f=3,p=4,n=0,h=0]
[Result of search is]
class(A,mammal) :- has_milk(A).
[4 redundant clauses retracted]

[Generalising class(trout,fish).]
[Most specific clause is]
class(A,fish) :- has_gills(A), has_covering(A,scales), has_legs(A,
	0), has_eggs(A), habitat(A,water).
[C:-7,4,11,0 class(A,fish).]
[C:3,4,0,0 class(A,fish) :- has_gills(A).]
[2 explored search nodes]
[f=3,p=4,n=0,h=0]
[Result of search is]
class(A,fish) :- has_gills(A).
[4 redundant clauses retracted]

[Generalising class(lizard,reptile).]
[Most specific clause is]
class(A,reptile) :- has_covering(A,scales), has_legs(A,4), has_eggs(A),
	habitat(A,land).
[C:-5,5,10,0 class(A,reptile).]
[C:2,5,2,0 class(A,reptile) :- has_covering(A,scales).]
[C:2,4,0,0 class(A,reptile) :- has_covering(A,scales), has_legs(A,4).]
[C:1,5,2,0 class(A,reptile) :- has_covering(A,scales), has_eggs(A).]
[C:2,4,1,0 class(A,reptile) :- has_legs(A,4).]
[C:-3,5,7,0 class(A,reptile) :- has_eggs(A).]
[C:0,4,3,0 class(A,reptile) :- habitat(A,land).]
[7 explored search nodes]
[f=2,p=4,n=0,h=0]
[Result of search is]
class(A,reptile) :- has_covering(A,scales), has_legs(A,4).
[4 redundant clauses retracted]

[Generalising class(snake,reptile).]
[Most specific clause is]
class(A,reptile) :- has_covering(A,scales), has_legs(A,0), has_eggs(A),
	habitat(A,land).
[C:-8,2,10,0 class(A,reptile).]
[C:-1,2,2,0 class(A,reptile) :- has_covering(A,scales).]
[2 explored search nodes]
[f=-1,p=2,n=2,h=0]
[No compression]

[Generalising class(eagle,bird).]
[Most specific clause is]
class(A,bird) :- has_covering(A,feathers), has_legs(A,2), homeothermic(A),
	has_eggs(A), habitat(A,land), habitat(A,air).
[C:-8,3,11,0 class(A,bird).]
[C:2,3,0,0 class(A,bird) :- has_covering(A,feathers).]
[2 explored search nodes]
[f=2,p=3,n=0,h=0]
[Result of search is]
class(A,bird) :- has_covering(A,feathers).
[3 redundant clauses retracted]

class(snake,reptile).
class(A,mammal) :- has_milk(A).
class(A,fish) :- has_gills(A).
class(A,bird) :- has_covering(A,feathers).
class(A,reptile) :- has_covering(A,scales), has_legs(A,4).
[Total number of clauses = 5]

yes
[:- generalise(class/2)? - Time taken 0.32s]

======
Another request for a listing demonstrates the changes made by
generalisation.
======

|- listing(class/2)?
class(snake,reptile).
class(A,mammal) :- has_milk(A).
class(A,fish) :- has_gills(A).
class(A,bird) :- has_covering(A,feathers).
class(A,reptile) :- has_covering(A,scales), has_legs(A,4).
yes
[:- listing(class/2)? - Time taken 0s]

======
Generalisation of the predicate false is carried out below.
======

|- generalise(false)?
[Generalising :- class(trout,mammal).]
[Most specific clause is]
:- class(A,mammal), class(A,fish), has_gills(A), has_covering(A,
	scales), has_legs(A,0), has_eggs(A), habitat(A,water).
[C:40,42,1,0 :- class(A,mammal).]
[C:5,7,0,0 :- class(A,mammal), class(A,fish).]
[C:39,42,1,0 :- class(A,mammal), has_legs(A,0).]
[C:39,42,1,0 :- class(A,mammal), has_eggs(A).]
[C:39,42,1,0 :- class(A,mammal), habitat(A,water).]
[C:38,42,1,0 :- class(A,mammal), has_eggs(A), habitat(A,water).]
[C:38,42,1,0 :- class(A,mammal), has_legs(A,0), habitat(A,water).]
[7 explored search nodes]
[f=5,p=7,n=0,h=0]
[Result of search is]
:- class(A,mammal), class(A,fish).
[7 redundant clauses retracted]

[Generalising :- class(lizard,mammal).]
[Most specific clause is]
:- class(A,mammal), class(A,reptile), has_covering(A,scales),
	has_legs(A,4), has_eggs(A), habitat(A,land).
[C:34,36,1,0 :- class(A,mammal).]
[C:6,8,0,0 :- class(A,mammal), class(A,reptile).]
[C:33,36,1,0 :- class(A,mammal), has_legs(A,4).]
[C:33,36,1,0 :- class(A,mammal), has_eggs(A).]
[C:33,36,1,0 :- class(A,mammal), habitat(A,land).]
[C:32,36,1,0 :- class(A,mammal), has_legs(A,4), habitat(A,land).]
[6 explored search nodes]
[f=6,p=8,n=0,h=0]
[Result of search is]
:- class(A,mammal), class(A,reptile).
[8 redundant clauses retracted]

[Generalising :- class(eagle,mammal).]
[Most specific clause is]
:- class(A,mammal), class(A,bird), has_covering(A,feathers), 
	has_legs(A,2), homeothermic(A), has_eggs(A), habitat(A,
	land), habitat(A,air).
[C:27,29,1,0 :- class(A,mammal).]
[C:5,7,0,0 :- class(A,mammal), class(A,bird).]
[C:26,29,1,0 :- class(A,mammal), has_legs(A,2).]
[C:26,29,1,0 :- class(A,mammal), homeothermic(A).]
[C:26,29,1,0 :- class(A,mammal), has_eggs(A).]
[C:26,29,1,0 :- class(A,mammal), habitat(A,land).]
[C:26,29,1,0 :- class(A,mammal), habitat(A,air).]
[C:25,29,1,0 :- class(A,mammal), homeothermic(A), has_eggs(A).]
[C:25,29,1,0 :- class(A,mammal), homeothermic(A), habitat(A,land).]
[C:25,29,1,0 :- class(A,mammal), homeothermic(A), habitat(A,air).]
[C:25,29,1,0 :- class(A,mammal), has_legs(A,2), homeothermic(A).]
[C:25,29,1,0 :- class(A,mammal), has_legs(A,2), has_eggs(A).]
[C:25,29,1,0 :- class(A,mammal), has_legs(A,2), habitat(A,air).]
[13 explored search nodes]
[f=5,p=7,n=0,h=0]
[Result of search is]
:- class(A,mammal), class(A,bird).
[7 redundant clauses retracted]

[Generalising :- class(lizard,fish).]
[Most specific clause is]
:- class(A,fish), class(A,reptile), has_covering(A,scales), has_legs(A,
	4), has_eggs(A), habitat(A,land).
[C:21,23,1,0 :- class(A,fish).]
[C:5,7,0,0 :- class(A,fish), class(A,reptile).]
[C:20,23,1,0 :- class(A,fish), has_covering(A,scales).]
[C:20,23,1,0 :- class(A,fish), has_eggs(A).]
[C:19,23,1,0 :- class(A,fish), has_covering(A,scales), has_eggs(A).]
[5 explored search nodes]
[f=5,p=7,n=0,h=0]
[Result of search is]
:- class(A,fish), class(A,reptile).
[7 redundant clauses retracted]

[Generalising :- class(eagle,fish).]
[Most specific clause is]
:- class(A,fish), class(A,bird), has_covering(A,feathers), has_legs(A,
	2), homeothermic(A), has_eggs(A), habitat(A,land), habitat(A,
	air).
[C:15,17,1,0 :- class(A,fish).]
[C:4,6,0,0 :- class(A,fish), class(A,bird).]
[C:14,17,1,0 :- class(A,fish), has_eggs(A).]
[3 explored search nodes]
[f=4,p=6,n=0,h=0]
[Result of search is]
:- class(A,fish), class(A,bird).
[6 redundant clauses retracted]

[Generalising :- class(eagle,reptile).]
[Most specific clause is]
:- class(A,reptile), class(A,bird), has_covering(A,feathers),
	has_legs(A,2), homeothermic(A), has_eggs(A), habitat(A,
	land), habitat(A,air).
[C:10,12,1,0 :- class(A,reptile).]
[C:5,7,0,0 :- class(A,reptile), class(A,bird).]
[C:9,12,1,0 :- class(A,reptile), has_eggs(A).]
[C:9,12,1,0 :- class(A,reptile), habitat(A,land).]
[C:8,12,1,0 :- class(A,reptile), has_eggs(A), habitat(A,land).]
[5 explored search nodes]
[f=5,p=7,n=0,h=0]
[Result of search is]
:- class(A,reptile), class(A,bird).
[7 redundant clauses retracted]

:- class(A,mammal), class(A,fish).
:- class(A,mammal), class(A,reptile).
:- class(A,mammal), class(A,bird).
:- class(A,fish), class(A,reptile).
:- class(A,fish), class(A,bird).
:- class(A,reptile), class(A,bird).
[Total number of clauses = 6]

yes
[:- generalise(false)? - Time taken 1.63s]

======
Another request for a listing demonstrates the changes made by
generalisation.
======

|- listing(false)?
:- class(A,mammal), class(A,fish).
:- class(A,mammal), class(A,reptile).
:- class(A,mammal), class(A,bird).
:- class(A,fish), class(A,reptile).
:- class(A,fish), class(A,bird).
:- class(A,reptile), class(A,bird).
[Total number of clauses = 6]
yes
[:- listing(false)? - Time taken 0.02s]

======
The query `listing?' without arguments gives the user-defined predicates.
======

|- listing?
The following user predicates are defined:
  animal/1       class/1        class/2        covering/1     habitat/1
  habitat/2      has_covering/2 has_eggs/1     has_gills/1    has_legs/2
  has_milk/1     homeothermic/1
[Total number of clauses = 110]
yes
[:- listing? - Time taken 0.00s]

======
User-defined predicates can be queried as follows.
======

|- class(trout,X)?
X = fish ;
no
[:- class(trout,X)? - Time taken 16ms]
|- ^D

======
The session is closed using ^D (end of file).
======