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<== Date ==> <== Thread ==>

Subject: Internal type conversion in Epics
From: Andy Foster <ajf@ast.cam.ac.uk>
To: Epics Questions <tech-talk@aps.anl.gov>
Date: Wed, 19 Jul 1995 15:08:01 +0100 (BST)
Marty,

Thanks for your reply concerning the accuracy of
converting a Double to a String within EPICS.
I have done some further investigation and found that
by setting PREC to 7 in the incoming record (the record
which is receiving the double), I do indeed get an accuracy
of 7 decimal places. However, changing PREC to 15 (which you
might want for the accuracy of a double), 
I discovered that the double goes through with an
accuracy of only 5 decimal places!

The problem lies within the code for "cvtDoubleToString" inside
libCom/cvtFast.c. Line 150 of cvtFast.c shows that the value will
be converted to a string as follows, whenever PREC > 8.

sprintf(pstr_value,"%12.5e\0",flt_value);

I would say that "%12.5e" format is not what we want in
this case. Are there any plans to change this to something
which greater reflects the accuracy expected of a double?

Andy

==========================================================================
Andy Foster
Royal Greenwich Observatory		Tel:    44 (0)1223 374899 (direct)
Madingley Road				E-mail: ajf@ast.cam.ac.uk
Cambridge
CB3 0HA
UK


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