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RE: Diffraction Program and Data Standards



John Quintana writes:

>During the last Beamline Meeting, I mentioned that UNI-CAT and DND-CAT are 
>beginning to collaborate on a diffraction program with the front end 
>provided by TCL/TK.  A fall back program would be super with TCL/TK 
>built in which would be done with Robert Fleming.  Now that people have 
>had a week to mull this over in the back of their minds, I was just wondering 
>if other groups would be willing to participate in this effort and/or
>would like to use the results of this collaborations on their beamlines.

I would be very interested in getting the specifications for the diffraction
routines which you plan to write in C, and to code them in IDL. I think the
effort required to code/maintain in IDL is so much less than C that I will try
to do as much as possible in IDL. The graphics basically come for free, while
they will be difficult in C, since one will have to use graphics libraries
which may not be portable. If the graphics are not built into the diffraction
program one needs to worry about data access (via a file).

The IDL syntax is very user friendly. A scan command can be implemented like

IDL> scan, 'two-theta', start=40, stop=50, step=.01, time=0.1

Keyword parameters are much easier to remember than positional ones, and the
keywords do not need to be entered in any particular order. Scan parameters
can default to their previous values, with the user prompted for
missing/non-defaulted values.

It is certainly worth considering prototyping in IDL before coding in C. IDL
is much more portable than C if one is writing programs with graphics.
Graphics libraries (with widgets) which run on Unix, VMS, DOS and Mac are hard
to find!

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