Changes for page Code Example: Data Structure Style vs. Object Style

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...	...	@@ -7,15 +7,17 @@
7	7
8	8	### Data Structure Style
9	9
10		- type Square struct {
	10	+ interface GeometricObject {}
	11	+
	12	+ class Square implements GeometricObject {
11	11	length float
12	12	}
13	13
14		- type Circle struct {
	16	+ class Circle implements GeometricObject {
15	15	radius float
16	16	}
17	17
18		- func Circumference(g Object) float {
	20	+ function Circumference(g GeometricObject) float {
19	19	switch type(g):
20	20	case Square:
21	21	return 4 * g.length
...	...	@@ -23,7 +23,8 @@
23	23	return 2 * PI * g.radius
24	24	}
25	25
26		-1.
	28	+1. Adding an Area() function with a very similar anatomy to Circumference() is easy because it only requires adding new code.
	29	+1. Adding a new datatype, Rectangle, is harder because it requires touching existing code, namely any functions like Circumference() or Area() that need to be enabled handle this datatype.
27	27
28	28	####
29	29
...	...	@@ -56,3 +56,11 @@
56	56	return 2 * PI * this.radius
57	57	}
58	58	}
	62	+
	63	+1. Adding a function Area() to the GeometricObject interface is hard because it requires touching existing code, namely extending all Square and Circle classes with the new function.
	64	+1. Adding a new datatype, Rectangle, is easy because only new code is added, namely a Rectangle class.
	65	+
	66	+### Conclusion
	67	+
	68	+* The lesson learned here is that data structures are easy to extend with functions, and objects are easy to extend with data types.
	69	+* Although the difference between the two styles may seem insignificant in this simplified example, it has serious implications in complex production codebases with multiple data types and behaviors.