Can I Always Change the Order of Operands of Logical Operators?

Question

Rightia Rollmann 2016-8-16

1
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/299790-can-i-always-change-the-order-of-operands-of-logical-operators

编辑： James Tursa 2016-8-16

Is there any case that writing the operands of logical operators with different order make a different result? (A = B and B = A are totally different and not interchangeable)

Are A == B and B == A always the same?

Are A >= B and B =< A always the same?

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Star Strider 2016-8-16

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/299790-can-i-always-change-the-order-of-operands-of-logical-operators#answer_231944

Yes. They’re commutative.

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

请先登录，再进行评论。

Answer 2

Sean de Wolski 2016-8-16

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/299790-can-i-always-change-the-order-of-operands-of-logical-operators#answer_231945

编辑：Sean de Wolski 2016-8-16

Yes, with the exception of short circuiting behavior with || and &&. In which case the second expression may not run.

http://www.mathworks.com/help/releases/R2016a/matlab/ref/logicaloperatorsshortcircuit.html#bt_0nai-1

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

请先登录，再进行评论。

Answer 3

James Tursa 2016-8-16

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/299790-can-i-always-change-the-order-of-operands-of-logical-operators#answer_231946

编辑：James Tursa 2016-8-16

在 MATLAB Online 中打开

(Semantics, == and >= and <= are "relational" operators, not "logical" operators. E.g. & and | are "logical" operators.)

For the built-in numeric and logical and char types, I can think of no situation where your relational examples would give a different result ... even when considering inf and NaN situations. But for OOP classes, of course, the behavior could be different depending on how the underlying overloaded code is written. E.g., if the < operator was coded to be the complement of the >= operator, you could get some unexpected results that were not the same:

>> A = 5;
>> B = 6;
>> A < B
ans =
     1
>> B > A
ans =
     1
>> ~(A >= B)
ans =
     1       <-- Same result as A < B
>> A = inf
A =
   Inf
>> B = NaN
B =
   NaN
>> A < B
ans =
     0
>> B > A
ans =
     0
>> ~(A >= B)
ans =
     1       <-- NOT the same result as A < B