Add More Primitives

00:00 Adding More Primitives. Two other primitives closely related to a line are SVG polylines and polygons, which extend the idea of a line. They’re both tuples of two or more points, which look nearly identical.

00:23 The difference is that a polygon is closed, meaning that it connects the first and last point, while the polyline isn’t, leaving the last point unconnected.

00:32 In case you’re wondering, the points parameter must be passed as a keyword argument to avoid conflating it with the value positional argument.

01:02 Sometimes it may be more convenient to combine existing lines instead of individual points, especially when they don’t form a continuous polyline. That’s when a DisjointLines primitive comes in handy.

01:30 Note that this is merely a logical collection of lines and has no SVG equivalent. Other, more specific SVG primitives that you’ll be interested in include a rectangle and a text element.

01:42 You implement them as data classes rather than tuples or named tuples because they’re not inherently sequences of elements. The rectangle accepts an optional top-left corner, whose coordinates get mixed in with the rest of the attributes through the union operator (|).

03:03 Last but not least, you’ll apply the null object pattern again by implementing a dummy NullPrimitive, which returns an empty string. This will let you avoid checking for a special case when there are no primitives to represent something in SVG, ultimately leading to cleaner and more readable code.

03:37 In the next section of the course, you’ll put your primitives to use by decomposing various border patterns around the maze squares into SVG elements.