Not A Number/Path/Refnum? Function

LabVIEW 2018 Help

Edition Date: March 2018
Part Number: 371361R-01
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Owning Palette: Comparison Functions

Requires: Base Development System

Returns TRUE if number/path/refnum is not a number (NaN), <Not a Path>, or not a refnum. Otherwise, this function returns FALSE.

Use this function to make sure a reference to an object, such as a VI, application, or control, still resides in system memory and was not closed.

The connector pane displays the default data types for this polymorphic function.


number/path/refnum can be a scalar number, path, or refnum, or it can be a cluster or array of numbers, paths, or refnums.
NaN/Path/Refnum? is a Boolean value of the same data type structure as number/path/refnum.

Not A Number/Path/Refnum? Details

This function works only on references generated by LabVIEW functions. Do not use this function to determine the validity of a rendezvous refnum, semaphore refnum, or any refnum created by the GOOP wizard, LabVIEW Database Connectivity Toolkit, or LabVIEW Internet Toolkit. For rendezvous refnums, use the Not A Rendezvous VI. For semaphore refnums, use the Not A Semaphore VI. For all other GOOP refnums or toolkit refnums, use the Vis defined by the refnum creator.

To avoid race conditions when evaluating the refnum status, National Instruments recommends limiting the usage of this function in the following ways:

  • Do not use this function to evaluate whether a refnum is invalid before using the refnum.
  • Use this function in custom probes to get the refnum status.
  • Use this function to evaluate the status of an existing invalid refnum before evaluating a new refnum.
  • Use this function to evaluate the status of a refnum before using another refnum.
  • Consider using semaphores to protect code that the function executes conditionally.


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