On Wed, May 12, 2010 at 12:16 PM, Colin B.
[email protected] wrote:
it won’t end up with the arguments backwards.
and if <=> is defined for (a representation of) other and
(a representation of) self, that probably won’t work either!
Based on an earlier thread from the OP where the use case was
operations on integers and points, he might be concerned about my
pointing out (no pun intended) that, as far as I know, while there’s a
conventional meaning for multiplying a vector quantity (like a Point)
and a scalar quantity (like an Integer), there isn’t for adding or
subtracting a scalar and a vector.
So we need to allow
1 * Point.new(1,1)
but disallow
1 + Point.new(1, 1)
or
1 - Point.new(1,1)
One way to address this might be something like
class Point
attribute :x, :y
def initialize(x, y)
self.x, self.y = x, y
end
def +(value)
if Point === value
Point.new(x + value.x, y + value.y)
else
raise ArgumentError.new(“Attempt to add a point to a scalar”)
end
end
def -(value)
if Point === value
Point.new(x + value.x, y + value.y)
else
raise ArgumentError.new(“Attempt to subtract a point from a
scalar”)
end
end
def dot_product(other_point)
x*other_point.x + y * other_point.y
end
def (value)
if Point == value
dot_product(value)
else
Point.new(xvalue, y*value)
end
end
class ScalarWrapper
attribute :scalar_value
def initialize(scalar_value)
self.scalar_value = scalar_value
end
def +(value)
raise ArgumentError.new("Attempt to add scalar to a point")
end
def -(value)
raise ArgumentError.new("Attempt to subtract a scalar from a
point")
end
def *(other_point)
Point.new(scalar_value*other_point.x,
scalar_value*other_point.x)
end
end
end
def coerce(other)
[Point::ScalarWrapper.new(other), self]
end
end
–
Rick DeNatale
Blog: http://talklikeaduck.denhaven2.com/
Github: rubyredrick (Rick DeNatale) · GitHub
Twitter: @RickDeNatale
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