On 1 Apr 2008, at 3:51 am, iliali16 wrote:
so my question is if this is ok to represent a map. If yes I will
try to
write the function which makes it 4 x 4 myself. What I jsut need as an
answer is Yes or No. Just to let you know is that I am trying to
build the
Wumpus World
What you should know is that there is no rule that the Wumpus World
has to be 4 x 4. Quoting
http://web.inf.tu-dresden.de/~mit/LRAPP/wumpus/wumpus.htm
"The size of the grid may vary for different scenarios."
You are tacitly assuming that if you want to know what's where in the
wumpus world you have to store an *image* of that world. But this is
not so.
The wumpus may be dead, in which case we don't care where it is,
or it may be in some specific location:
wumpus :: Maybe Location
The gold may have been grabbed, in which case we know where it is
without looking (we have it), or it may be in some specific place:
gold :: Maybe Location
In some versions of the wumpus world, there may be more than one
piece of gold. In that case,
gold :: [Location]
There is some number of pits. There might be none. All we really
want to know is whether a particular square is a pit or not.
is_pit :: Location -> Bool
It's not clear to me whether the gold or the wumpus might be in a
pit. Since it's deadly to enter a pit anyway, we don't really care.
The gold and the wumpus might well be in the same cell.
So we can do this:
type Location = (Int, Int)
data Wumpus_World
= Wumpus_World {
bounds :: Location,
wumpus :: Maybe Location,
gold :: Maybe Location,
is_pit :: Location -> Bool
}
initial_world = Wumpus_World {
bounds = (4,4),
wumpus = Just (3,3),
gold = Just (3,3),
is_pit = \loc -> case loc of
(2,1) -> True
(4,3) -> True
_ -> False
} -- I just made this one up
holds :: Eq a => Maybe a -> a -> Bool
holds (Just x) y = x == y
holds (Nothing) _ = False
has_wumpus, has_gold :: Wumpus_World -> Location -> Bool
has_wumpus world location = wumpus world `holds` location
has_gold world location = wumpus world `holds` location
There are lots of other ways to do this, and whether this is a
good one depends on what you need to do with it. It might be
better to have
has_wumpus :: Location -> Bool
has_gold :: Location -> Bool
as the field members directly, for example. One thing that is
right about it is that it doesn't build in any specific idea of
the size of the world. Another good thing is that it postpones
the decision about how to tell where the pits are.
But of course there are two maps: the complete map of how the world
really is, which the world simulator has to have, and the "agent's"
partial map recording what it has seen so far. They might have
similar representations, or they might not.
It's a really good idea to write as much of the code as you can so
that it doesn't know what the map representation is.
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