June Kim wrote:
> http://www.amzi.com/articles/prolog_fun.htm (look for "animals")
> What is the general approach in J with this type of tree
> structure problem(I think I have seen an APL2 implementation
> a few months ago but didn't read it carefully since I don't
> understand APL)? Does anyone have a reference program of Animals
> in J?
Here is how I might implement "animals" in J.
Notes:
The initial functions I defined are a bit more
elaborate than I really need, because I did not have
the full program architecture developed at the time I
wrote them, and I didn't care to go back and reduce
the program.
Rather than a loop asking the person if they want
to continue, I elected to make the verb 'go' only
ask one series of questions. It's simple enough to type
go'' again if you want to deal with another set of
questions about some animal. (It would also be simple
to add another level of looping, but I found this
approach more convenient.)
I did not use a "tree", as such. Instead, I used a list
of questions, a list of animals, and a corresponding
table of known facts: Given a question and an animal,
would the answer be yes, no or maybe (where "maybe" really
means "I don't know what the answer would be")?
"Animals" doesn't say what should happen if at one point
in time an animal is said to have some feature and at
another point in time an animal is said to not have that
feature. I elected to throw an error for those cases.
Conceivably you could invalidate earlier q&a sessions with
answers received in those sessions being hints at possible
answers but not necessarily true. However, this would be
more complicated to implement.
--
Raul
Know=:0 0$Animals=:Questions=:''
NB. x is boxed strings
NB. y is integers (return it),
NB. or boxed strings (find its index in x)
NB. or a string (find index of boxed string in x)
index=:4 :0"1
select. {.0#y
case. 0 do. y
case. a: do. x i.y
case. ' ' do. x i.<y
end.
)
animal=:3 :0
if.0=#y do. y return.end.
r=. Animals index y
if. r = #Animals do.
Animals=: Animals,<y
Know=: Know,.'M'
end. r
)
question=:3 :0
if.0=#y do. y return.end.
r=. Questions index y
if. r = #Questions do.
assert. 0<#y
Questions=: Questions,<y
Know=: Know,'M'
end. r
)
NB. assert that question x is true for animal y
has=:4 :0
q=. question x
a=. animal y
Know=: 'Y' (<q,a)} Know
)
NB. invert yes/no/maybe truth value
not=: 3 :0
('YNM'i.y){'NYM'
)
NB. merge yes/no/maybe values
merge=:4 :0"0
r=. -.&'M' ~.x,y
'contradiction' assert 2>#r
{.r,'M'
)
NB. y is animals;questions;answers
NB. remember that those questions have
NB. those answers for those animals
learn=:3 :0
a=. animal 0{::y
q=. question 1{::y
b=. 2{::y
if.#b do.
inds=. q <@,"0 a
Know=: (b merge inds { Know) inds} Know
end.
)
NB. find the most interesting remaining question,
NB. given asked questions x and possible animals y
interesting=:4 :0
q=. (?~#Questions) -. question x
if. 0=#q do. q return.end.
a=. animal y
rating=. 'Y' *&.>:&([: +/"1 =&(q{a{"1 Know)) 'N'
if. 0=best=.>./rating do. i.0 return.end.
q {~ rating i. best
)
NB. delete extra blanks
deb=:3 :0
}:}.(#~ ' ' [EMAIL PROTECTED] ])' ',y,' '
)
NB. prompt is not compatible between jconsole
NB. and windowed j. This is an attempt to work
NB. around that problem.
NB. Also, jbreak will not interrupt prompt in
NB. windowed j. As an emergency escape, a two space
NB. response will force an error.
query=:3 :0
require 'misc'
r=. prompt y
t=. y }.~ LF i:~ LF,y
if. t=(#t) {. r do.
r=. (#t)}.r
end.
assert. -.r-:' '
deb r
)
NB. ask a yes or no question
ask=:3 :0
whilst. ' '=yn do.
yn=. {.-.&' ' 'YNYN '{~'ynYN'i.query y
end. yn
)
NB. english reference to animal
anAnimal=:3 :0
('a',((tolower{.a)e.'aeiou')#'n'),' ',a=.y {:: Animals
)
NB. confirm that we've guessed (or not) the right animal
NB. x is list of asked questions, for learning purposes
confirm=:4 :0
t=.'N'
other=.'the other animals'
note=.''
pick=.{.y
if.0<#y do.
other=. anAnimal pick
t=.ask 'Is it ',other,'? '
if. 'Y'=t do. learn ({.y);x end.
else.
note=.'I give up.',CRLF
end.
if.t='N' do.
a=.animal tmp=.query note,'What animal were you thinking of? '
learn a;x
this=.anAnimal a
q1=.'What is a yes/no question that distinguishes'
q2=. this,' from ',other,'? '
q=.question '? ',~-.&'?' query q1,CRLF,q2,CRLF
final=.ask 'For ',this,': ',CRLF,' ',q {:: Questions
learn a;q;final
learn pick;q;not final
end.
)
NB. use go'' to begin q&a session about an animal
go=:3 :0
R=.?~#Animals NB. possible animals
Q=.'' NB. asked questions
A=.'' NB. corresponding answers
while. (1<#R) *. 0<#q=. Q interesting R do.
A=.A,a=. ask q {:: Questions
R=.R -. I. (not a) = q{Know
Q=.Q,q
end.
(Q;A) confirm R
''
)
NB. some sample initial knowledge:
learn (animal'mouse');(question'Does it have fur? ');'Y'
learn (animal'lizard');(question'Does it have fur? ');'N'
NB. diagnostic routine: display current knowledge:
know=:3 :0
('';Animals),Questions,.]&.>Know
)
NB. end.
----------------------------------------------------------------------
For information about J forums see http://www.jsoftware.com/forums.htm
