Lua 逻辑运算符
示例
在Lua中，可以通过逻辑运算符来操作布尔值。这些运营商包括not，and，和or。
用简单的表达式，结果非常简单：
print(not true) --> false print(not false) --> true print(true or false) --> true print(false and true) --> false
优先顺序
优先顺序类似于一元数学运算符-，*以及+：
not
然后and
然后or
这可能导致复杂的表达式：
print(true and false or not false and not true)
print( (true and false) or ((not false) and (not true)) )
--> these are equivalent, and both evaluate to false快捷评估
运算符，and并且or可能仅使用第一个操作数进行评估，前提是不需要第二个：
function a()
print("a() was called")
return true
end
function b()
print("b() was called")
return false
end
print(a() or b())
--> a() was called
--> true
-- nothing else
print(b() and a())
--> b() was called
--> false
-- nothing else
print(a() and b())
--> a() was called
--> b() was called
--> false惯用条件运算符
由于逻辑运算符的优先级，因此可以在Lua中使用快捷条件评估和对as进行非false和非nil值评估的功能true：惯用条件运算符：
function a()
print("a() was called")
return false
end
function b()
print("b() was called")
return true
end
function c()
print("c() was called")
return 7
end
print(a() and b() or c())
--> a() was called
--> c() was called
--> 7
print(b() and c() or a())
--> b() was called
--> c() was called
--> 7此外，由于性质xandaorb结构，a将永远不会被退还，如果它的计算结果false，这一条件将随后始终返回b无论是什么x是。
print(true and false or 1) -- outputs 1