Please report any errors to me at pearce@mathcs.sjsu.edu. Thanks.

page 136: Arguments to point? in definition of point+ should be point1 instead of p1 and point2 instead of p2.

page 145: Missing parenthesis to end definition of self inside make-point.. Also, point is assumed to have been defined
as previously:

   (define point 'point)

page 146. argument to point? in definition of xc should be point, not val.