（cond1&& cond2&& cond3）总是从左到右评估？ [英] Does (cond1 && cond2 && cond3) always evaluate left to right?
问题描述
你好
假设我想检查object1.Property1是否等于某个值，但
object1可能为null。
目前我有这样的代码：
if（object1！= null）
{
if（object1.Property == desiredValue）
{
//在这里工作
}
}
这是我的问题 - 我可以这样做吗...
if（object1！= null&& object1。物业== desiredValue）
{
//在这里工作
}
.. ..并确保条件总是从左到右评估和
一旦条件评估为假，评估就会停止？
如果我可以崩溃条件转换为if if语句，您认为
这或多或少是优雅的编码吗？
TIA
Bill
Hi There
Say I want to check if object1.Property1 is equal to a value, but
object1 could be null.
At the moment I have code like this:
if (object1 != null)
{
if (object1.Property == desiredValue)
{
//Do work here
}
}
Here is my question - Can I do this ...
if (object1 != null && object1.Property == desiredValue)
{
//Do work here
}
.... and be sure that conditions are always evaluated left to right and
the evaluation stops as soon as a condition evaluates to false ?
If I can collapse the conditions into one if statement, do you think
this is more or less elegant coding?
TIA
Bill
推荐答案
是的，你可以。
这些陈述是evalueat从左到右。最正确的条件
在以前的条件之一评估为假时不会被评估。
或******* @ yahoo。 com.au"写道：
Yes, you can.
The statements are evalueated from left to right. The most right condition
is not evaluated when one of the former conditions evaluates to false.
"or*******@yahoo.com.au" wrote:
你好
说我想检查object1.Property1是否等于一个值，但
object1可能为null。
目前我有这样的代码：
if（object1！= null）
{
if（object1.Property == desiredValue）
{
//在这里工作
}
}
这是我的问题 - 我可以这样做吗......
if（object1！= null&& object1.Property == desiredValue）
{
//在这里工作
}
....确保条件总是从左到右评估，并且一旦条件评估为假，评估就会停止？
如果我可以将条件合并到一个if语句中，你认为<这或多或少是优雅的编码？
比尔
Hi There
Say I want to check if object1.Property1 is equal to a value, but
object1 could be null.
At the moment I have code like this:
if (object1 != null)
{
if (object1.Property == desiredValue)
{
//Do work here
}
}
Here is my question - Can I do this ...
if (object1 != null && object1.Property == desiredValue)
{
//Do work here
}
.... and be sure that conditions are always evaluated left to right and
the evaluation stops as soon as a condition evaluates to false ?
If I can collapse the conditions into one if statement, do you think
this is more or less elegant coding?
TIA
Bill
谢谢Marinus
Thanks Marinus
此外，nte在原始中指定了此行为nal C语言
定义，并转入C ++，Java和C＃。这对于一个特定的编译器来说并不是特别的，但是要求任何编译器实现
任何一个C系列语言。
-
-
真相，
James Curran
[以前的VC ++ MVP]
主页： www.noveltheory.com 工作： www.njtheater.com
博客： www.honestillusion.com 日工作： www.partsearch.com
<或******* @ yahoo.com.au>在消息中写道
news：11 ********************** @ g47g2000cwa.googlegr oups.com ...
Also, nte that this behavior was specified in the original C language
definition, and carried over into C++, Java and C#. This is not particular
to one specific compiler, but a requirement for any compiler implementing
any of the C family of langauges.
--
--
Truth,
James Curran
[erstwhile VC++ MVP]
Home: www.noveltheory.com Work: www.njtheater.com
Blog: www.honestillusion.com Day Job: www.partsearch.com
<or*******@yahoo.com.au> wrote in message
news:11**********************@g47g2000cwa.googlegr oups.com...
你好
说我想检查object1.Property1是否等于一个值，但
object1可能为null。
目前我有这样的代码：
if（object1！= null）
{
if（object1.Property == desiredValue）
//在这里工作
}
}
这是我的问题 - 我可以这样做吗......
if（object1！= null&& ; object1.Property == desiredValue）
{
//在这里工作
}
...并确保条件始终从左到右评估
一旦条件评估为假，评估就会停止？
如果我可以将条件折叠成一个if语句，你认为这或多或少是优雅的编码吗？
TIA
Bill
Hi There
Say I want to check if object1.Property1 is equal to a value, but
object1 could be null.
At the moment I have code like this:
if (object1 != null)
{
if (object1.Property == desiredValue)
{
//Do work here
}
}
Here is my question - Can I do this ...
if (object1 != null && object1.Property == desiredValue)
{
//Do work here
}
... and be sure that conditions are always evaluated left to right and
the evaluation stops as soon as a condition evaluates to false ?
If I can collapse the conditions into one if statement, do you think
this is more or less elegant coding?
TIA
Bill
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