“和”、“或”背后有什么智慧吗？ Ruby 中的运算符？
我想知道为什么 ruby 的 and 、 or 优先级低于 && 、 || 和赋值运算符？有什么理由吗？
I wonder why ruby give and, or less precedence than &&, || , and assign operator? Is there any reason?
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我的猜测是这是 Perl 的直接继承。运算符
or和and后来在 Perl 5 中添加，用于需要较低优先级的特定情况。例如，在 Perl 中，这里我们希望
||具有较低的优先级，以便我们可以编写：并确保
||不会吞噬部分内容的行动。 Perl 5 引入了or，这是||的新版本，优先级较低，正是为了这个目的。在 Ruby 中，您可以使用
或但不能使用||的示例：如果您使用
||，则会出现语法错误。My guess is that's a direct carry-over from Perl. The operators
orandandwere added later in Perl 5 for specific situations were lower precedence was desired.For example, in Perl, here we wish that
||had lower precedence, so that we could write:and be sure that the
||was not going to gobble up part of the action. Perl 5 introducedor, a new version of||that has low precedence, for exactly this purpose.An example in Ruby where you could use
orbut not||:If you used
||, it would be a syntax error.区别在于优先级。
||、&&的优先级高于=，但and、or有较低的。因此，虽然您可以这样做：但您必须这样做：
才能获得相同的效果。如果这样做：
表达式的结果仍为 0，但值将为 nil。
The difference is precedence.
||,&&have higher precedence than=, butand,orhave lower. So while you can do:You would have to do:
to get same effect. If you do:
The result of expression would still be 0, but a value would be nil.
它们的优先级非常低，因此操作数不必用括号括起来，有时
&&和||就是这种情况。They have very low precedence so that the operands don't have to be wrapped in parentheses, as is sometimes the case with
&&and||.能够控制运算符的优先级有时很有用，特别是当您关心可读性时——条件语句中的额外括号有时会掩盖实际逻辑。
不过，坦率地说，我认为 Ruby 拥有布尔运算符优先级的原因主要源于这样一个事实：Matz 在编写 Ruby 之前是一名 Perl 程序员，并借用了该语言的大部分核心语法和运算符。
Being able to control the precedence of your operators is sometimes useful, especially if you are concerned with readability -- extra parenthesis in conditional statements can sometimes obscure the actual logic.
To be frank, though, I think the reason Ruby has the boolean operator precedence levels it does stems mostly from the fact that Matz was a Perl programmer before he ever wrote Ruby, and borrowed much of the core syntax and operators from that language.
我相信这个想法是专门让它们位于赋值运算符下方，这样您就可以使用赋值但不带括号来编写逻辑测试。
I believe the idea is specifically to get them below the assignment operators, so you can write logic tests with assignments but without parens.