Experimental Physics and Industrial Control System
I'm working on the International 8m Gemini Telescopes project
which is using EPICS for software control. I recently came
across the following problem and was wondering if anyone else
has experienced the same thing:
I have tried to pass down a double into a record which only
accepts strings. This record has been written especially for
the Gemini project and is known as a CAD record. Since
the CAD only accepts input strings, I had to do this by first
converting the double into a string using something like:
sprintf( pcad->inpa, "%0.15f", val );
Inside the routine that the CAD record calls, I had to do:
val = strtod( pcad->inpa, &c );
This worked fine but seems to be a bit of an overhead for
passing in a double!
I had previously thought that EPICS would do this sort of conversion
automatically. However, when I tried this I found that I lost a great
deal of accuracy in the value that I was passing in.
For example, I tried to pass 9.564328761234322 through
the output link of a double into the CAD input field. The result after:
val = strtod( pcad->inpa, &c );
was 9.564330000000000.
Is this what you would expect or am I missing something obvious
and important?
==========================================================================
Andy Foster
Royal Greenwich Observatory Tel: 44 (0)1223 374899 (direct)
Madingley Road E-mail: [email protected]
Cambridge
CB3 0HA
UK
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