fix bug in solution 4.3: use def not val in trait #74
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Exercise 4.1.4.3 Shaping Up 2 (Da Streets) had a bug. Using the code as it existed meant that `new Square(2.0).perimeter` was 0.0 (instead of 8.0) This occurred because the `override val perimeter = 2 * ...` was evaluated at the definition of trait Rectangular, rather than after creation of a new Square object. The definition of `perimeter` and `area` should have used `def` or `lazy val`; the preceding text recommended using `def` within `traits`. Hence the change.
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Exercise 4.1.4.3 Shaping Up 2 (Da Streets) had a bug.
Using the code as it existed meant that
new Square(2.0).perimeterwas 0.0 (instead of 8.0)
This occurred because the
override val perimeter = 2 * ...was evaluated at the definition of trait Rectangular, rather than after creation of a new Square object. The definition ofperimeterandareashould have useddeforlazy val; the preceding text recommended usingdefwithintraits. Hence the change.