请高手解答下这个语句的含义是什么？

liuzheyoungman

请高人帮忙解答下这个语句的含义是什么：if(!Data_Valid_P)
谢谢了！

zzt_1234

原帖由 liuzheyoungman 于 2011-1-11 11:02 发表

                               
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请高人帮忙解答下这个语句的含义是什么：if(!Data_Valid_P)
谢谢了！

如果没有压力值（我认为的）。

znon

Data_Valid_P is defined in the id.h header file, and is included in udf.h. The function returns 1 (true) if the data that is passed as an argument is valid, and 0 (false) if it is not.

You can check that the cell values of the variables that appear in your UDF are accessible before you use them in a computation by using the Data_Valid_P macro.

Suppose you read a case file and, in the process, load a UDF. If the UDF performs a calculation using variables that have not yet been initialized, such as the velocity at interior cells, then an error will occur. To avoid this kind of error, an if else condition can be added to your code. If ( if) the data are available, the function can be computed in the normal way. If the data are not available ( else), then no calculation, or a trivial calculation can be performed instead. Once the flow field has been initialized, the function can be reinvoked so that the correct calculation can be performed.

zzt_1234

原帖由 znon 于 2011-1-11 21:47 发表

                               
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Data_Valid_P is defined in the id.h header file, and is included in udf.h. The function returns 1 (true) if the data that is passed as an argument is valid, and 0 (false) if it is not.

You can chec ...

这么专业啊。呵呵。你也用udf吗？能请教一些问题嘛？

znon

这个就是帮助文件中的内容，我拷贝过来的。

有什么问题可以贴出来，大家互相学习。