?- consult('purple_r.pl').
true.

?- digit([one],[]).
true .

?- digit([un],[]).
false.

?- digit([uno],[]).
false.

?- sequence([fibonacci,numbers],Rest).
Rest = [numbers] .

?- sequence([hexagonal,numbers],Rest).
false.

?- operation([three,plus,two],[]).
true .

?- operation([three,plus,two,equals,five],[]).
false.

?- sentence([what,is,one,plus,one,?],[]).
true .

?- sentence([display,the,first,five,prive,numbers,.],[]).
false.

?- sentence([display,the,first,five,prime,numbers,.],[]).
true .

?- sentence([display,the,first,ten,prime,numbers,.],[]).
false.

?- recognizer.
|: what is six plus eight?
|: display the first three fibonacci numbers.
|: what is nine plus ten?
Error...
|: display the first six pentagonal numbers.
Error...
|: what is the square root of eight?
|: what is the square root of 8?
Error...
|: what is two to the third power?
|: what is 2 to the third power?
Error...
|:

?- sentence(S,[]).
S = [display, the, first, odd, number, '.'] ;
S = [display, the, first, even, number, '.'] ;
S = [display, the, first, natural, number, '.'] ;
S = [display, the, first, fibonacci, number, '.'] ;
S = [display, the, first, prime, number, '.'] ;
S = [display, the, first, triangular, number, '.'] ;
S = [display, the, first, two, odd, numbers, '.'] ;
S = [display, the, first, two, even, numbers, '.'] .

?- grs(Sentence).
Sentence = [what, is, two, minus, zero, ?] .

?- grs(Sentence).
Sentence = [what, is, one, to, the, sixth, power, ?] .

?- grs(Sentence).
Sentence = [what, is, five, plus, three, ?] .

?- grs(Sentence).
Sentence = [what, is, five, to, the, seventh, power, ?] .

?- grs(Sentence).
Sentence = [what, is, one, times, six, ?]
Unknown action:  for help)
Action?
Unknown action: [ (h for help)
Action?
Unknown action: A (h for help)
Action? .

?- grs(Sentence).
Sentence = [what, is, five, plus, eight, ?] .

?- prs
|    .
what is four plus seven?
true .

?- prs.
what is the factorial of zero?
true
Unknown action:  for help)
Action?
Unknown action: [ (h for help)
Action?
Unknown action: A (h for help)
Action? .

?- prs.
what is five minus three?
true .

?- prs.
what is seven to the nineth power?
true .

?- prs.
what is the factorial of eight?
true .