Experimental Physics and
Industrial Control System

From: Ralph Lange [mailto:[email protected]]
> Comparisons between numbers and non-numbers (such as NaN) are
> undefined.

Not quite: comparisons involving NaN are defined to always return false.  This means that a test of the form

	if (prec->drvl <= value && value <= prec->drvh)
	    // accept value
	else
	    // reject value

would have the desired effect (and setting a drv limit would cause all values to be rejected!)

> What is your suggestion on how to check limits for a non-number without
> using comparisons?
> 
> > We also found that you can type "NaN" at any entry field in DM2K
> which
> > writes NaN directly to the PV.
> 
> NaN, -inf and +inf are valid values for a double. Why would you reject
> entering valid values in entry fields?
> 
> Cheers,
> ~Ralph

Replies:

Re: NaN and analog records Dirk Zimoch

References:

NaN and analog records Benjamin Franksen

Re: NaN and analog records Goetz Pfeiffer

Re: NaN and analog records Ralph Lange

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