Experimental Physics and
Industrial Control System

"Allison, Stephanie" <[email protected]> · Fri, 11 Jun 2004 09:49:00 -0700

Hi,

> > I suggest the following:
> > PREC >= 0 means to format the value like printf("%.*f",PREC,VAL);
> > PREC < 0  means to format the value like printf("%.*e",-PREC,VAL);
> > 
> 
> I worry that there are a lot of tools out there that might 
> not take well to negative PREC values.

For edd/dm, specifying a negative precision in the graphic object properties means to use PREC from the database.  0 or greater means to use the user-specified value instead.  So edd/dm would have to change.

Here is a radical thought - it would be nice to have a new string field (ie, .FMT) that specifies how to display the value as a string.  Then I could set up the format of our vacuums (ie, VALs that should always be displayed using exponential notation) in the database instead of having to override the default display format in each client.  Also, some save/restore tools won't restore the proper values of things like vacuum limits unless you set a ridiculously large PREC.

BTW, in some legacy control systems (like the SLAC SLC control system), the right precision to use is determined based on the value using an algorithm that is better than the printf rules.  Mike Zelazny ported that algorithm from VMS Fortran to C++ in his channel watcher (so I don't have to worry about losing precision if I restore a channel watcher saveset during bumpless reboot).

Stephanie Allison

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System