Code Review – Bound Parameter

There is a piece of bad-smelling code, I happen to read today. The following aims to compute the angle between two line vectors.

There is a piece of bad-smelling code, I happen to read today. The following aims to compute the angle between two line vectors.

This code has been in the code repro for a long time, and it is brought to attention because of a failing unit test, where the input to the Math.acos function is bigger but very close to 1. Math.acos function returns Nan in this case.

Easy verification in Javascript:

js-math-acos

1

Math.acos(Math.max(Math.min(1, x), -1));

Math.acos(Math.max(Math.min(1, x), -1));

It is not elegant, but it works. If the precision is a high priority, we can create a class that stores the parts of the floating number (integer and fraction) using integer type. The integers do not lose precision and we need to implement the arithmetic operations e.g. how to carry over the values.

We also have the Math.Net library which provides a rich set of library regarding to Math vectors so this is totally re-inventing the wheel, however if this is a sandbox code, you may also consider operator overloading the vector type. The above code is easily error-prone because it is easy to mess up with the array indices.

You may also like: 代码审核之限制参数范围

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