When you have an easy way to express numeric literals, especially in hexadecimal, you can easily build flags that correspond to specific test cases, which is a common programming trick.
当您具有容易的方式来表达数值常量时，尤其是十六进制，就可以容易地构建对应于特定测试用例的标志，这是一种常见的编程技术。
Literals include strings and character and numeric literals.
文字量包括字符串，字符和数字文字量。
Note that numeric literals do not include a sign; a phrase like -1 is actually an expression composed of the operator - and the literal 1.
注意数值型的字面值不包括符号(译注：正负号)，像- 1实际上是个组合了一元运算符“-”和字面值1的表达式。
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