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243_MasterPieces_02b.qxd 4/18/03 6:59 PM Page 97

The Learning Brick Sorter • Masterpiece 2 97

If the program does not find a cell set to KB_YES, it scans the row again for the
value KB_UNKNOWN. In fact, given that there are no positive values, and that negative
values means,“don’t use this bin,” KB_UNKNOWN is our best second choice.
In theory, the routine should always find at least a KB_UNKNOWN value, unless the
user has provided inconsistent replies. However, as I said before, good programming prac-
tice states we should try to anticipate any possible users’ behavior.Thus, we have to
handle this case too, so lacking any guiding rule, the routine simply makes a random
choice.This makes our Learning Brick Sorter actually more adaptable. In fact, if the user
changes his mind while using the Learning Brick Sorter—giving a negative feedback to a
right choice—the user forces the Learning Brick Sorter to find a new solution to the
problem: that is, a different bin for that particular color.After a few cycles, the Learning
Brick Sorter will be trained to the new configuration.
Our next step is writing the routine that updates the knowledge base according to
the feedback provided by the user.

void UpdateKnowledgeBase(int ok)
{
int r;
// the user said OK
if (ok)
{
// this bin is the right one for the given range...
kb[range*3+bin]=KB_YES;
// ...and the wrong one for the other ranges
for(r=0;r<RANGES;r++)
if (r!=range)
kb[r*BINS+bin]=KB_NO;
}

// the user said NO
else
// the bin is the wrong one
kb[range*BINS+bin]=KB_NO;
}
This needs a few comments, as it reflects what I explained earlier when explaining
how the knowledge base works. When the user confirms that the bin was the correct
one, the program sets the corresponding cell of the knowledge base to KB_YES and the
other cells related to the same bin to KB_NO, meaning that no other colors can go into
that bin. When the user provides a negative feedback, the program simply sets the cell to
KB_NO. Notice that the value KB_UNKNOWN is never assigned to a cell: Every feed-
back turns at least one unknown status into a yes or a no.