lua - 为什么 "not nil"在 Lua 中返回 true？

Question

我使用 repl.it 来查看它返回的内容，只是出于好奇，结果发现不是零返回 true

为什么会这样？是不是因为在 Lua 中一切最终都应该是对的还是错的？

Repl.it 链接:https://repl.it/repls/SanePastelHarrier

Answer 1

因为 nil 在转换为 bool 值时是 false:

2.2 Booleans

The boolean type has two values, false and true, which represent the traditional boolean values. However, booleans do not hold a monopoly of condition values: in Lua, any value may represent a condition. Conditionals (such as the ones in control structures) consider both false and nil as false and anything else as true. Beware that, unlike some other scripting languages, Lua considers both zero and the empty string as true in conditional tests.

而 not 将其参数视为 bool 值:

3.3 Logical Operators

The logical operators areand, or, and not. Like control structures, all logical operators consider both false and nil as false, and anything else as true.