Multiple Assignment in Twoville
April 12, 2018 by Chris Johnson. Filed under
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public, twoville.
As I dream up animations in Twoville, I find myself generating a lot of shapes that share properties with other shapes. For instance, these two circles have the same radius and color:
a = circle()
b = circle()
a.radius = 10
b.radius = 10
a.rgb = [1, 1, 0]
b.rgb = [1, 1, 0]
I really wanted a way to express these repetitive assignments with less code. Something like Ruby’s Array.each method would have worked:
[a, b].each do |shape|
shape.radius = 10
shape.rgb = [1, 1, 0]
end
But even this seems too heavy to me. It introduces a new name—shape—that adds a layer of obfuscation. Then I wondered about setting the properties on the list:
a = circle()
b = circle()
[a, b].radius = 10
[a, b].rgb = [1, 1, 0]
This syntax makes me want to lick the screen. So concise and clear.
Arrays don’t otherwise support properties, so I was free to hijack their assignment. In the Twoville interpreter, this code effectively expands into the original code above. I haven’t quite figured out if I want the elements of the array to share references to a common right-hand side, or if each should have an independent copy.
I used multiple assignment to plot this checkerboard of squares:
And here’s the code behind it:
a = rectangle()
b = rectangle()
c = rectangle()
d = rectangle()
a.position = [100, 200]
b.position = [200, 100]
c.position = [100, 100]
d.position = [200, 200]
[a, b, c, d].size = [100, 100]
[a, b].rgb = [1, 0, 0]
[c, d].rgb = [0.2, 0.7, 0.7]