Line hierarchy of classes is useless about geometry

[fabianfiorotto]

A little hack ... but I still think that represent the same object with different classes is a bad idea

require 'geometry'
module Geometry

 class Line

    def interception(line)
        if line.vertical? && self.vertial? then
            return nil
        end

        if line.vertical? then
            m = self.slope
            c = self.intercept
            x = self.first.x
            y = m * x + c
            return Point[x,y]
        end
        if self.vertical? then
            m = line.slope
            c = line.intercept
            x = line.first.x
            y = m * x + c
            return Point[x,y]
        end

        m1 = self.slope
        m2 = line.slope
        c1 = self.intercept
        c2 = line.intercept
        return nil if m1 == m2
        x = (c2 - c1) / (m1 - m2)
        y = m1 * x + c1
        return Point[x,y]
    end

 end

 class TwoPointLine

    def intercept(axis=:y)
            y1 = first.y ; y2 = last.y
            x1 = first.x ; x2 = last.x
        case axis
        when :x
            return - y1 * (x2 - x1 ) / ( y2 - y1) + x1
        when :y
             return - x1 * (y2 - y1 ) / ( x2 - x1) + y1
        end
    end

    def vertical?
        x1 = first.x ; x2 = last.x
        x1 == x2
    end

    def horizontal?
        y1 = first.y ; y2 = last.y
        y1 == y2
    end

 end

 #test
 if __FILE__ == $0 then
     line1 = Line[[1,1],[3,3]]
     line2 = Line[[1,3],[3,1]]
     #it should be Point[2,2] in both cases
     p line1.interception(line2)
     p line2.interception(line1)
 end
end

[bfoz]

Thanks for looking into this. Line is implemented as a class cluster to avoid the conversion losses inherent in forcing all lines to be represented in the same way. Although, the current implementation does need a little cleaning.

I'm confused about what you're trying to implement here. Is this about adding an intersection method, or an intercept method?

[fabianfiorotto]

I need the intercept in order to implement my intersection method. You can ignore it if you don't like it but it would be nice to have one. but intercept method should be available for all the instances because is a property of the line, no matter how it has been generated.

[bfoz]

I've added an intercept method to all of the Line subclasses. Can you create a pull request for the intersection method?

[fabianfiorotto]

Should this method return a point or an array of points? If you are thinking in extend it to interception with polygons in the future it should return an array.

BtW. Can I close this issue? I created it for the intercept method and it's done now.

[bfoz]

I'm tempted to say it should return an Array, but Edge#intersection already returns a Point. Edge is more specialized (it was made for Polygon), so maybe that's ok. Either way, we can discuss this in another issue.