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International
Tables for Crystallography Volume G Definition and exchange of crystallographic data Edited by S. R. Hall and B. McMahon © International Union of Crystallography 2006 |
International Tables for Crystallography (2006). Vol. G. ch. 5.4, p. 536
Section 5.4.12.1. Programming style
a
Department of Mathematics and Computer Science, Kramer Science Center, Dowling College, Idle Hour Blvd, Oakdale, NY 11769, USA, and bSchool of Biomedical and Chemical Sciences, University of Western Australia, Crawley, Perth, WA 6009, Australia |
A traditional Fortran style of programming is used in CIFtbx. Common blocks are declared to report and control the state of the processing. This allows argument lists to be kept short and avoids the need to create complex data structure types, but introduces extensive `programming by side-effects'. In order to reduce the impact of this approach on users, two different views of the common blocks are provided. The declarations in ciftbx.cmn are needed by all users. The more extensive declarations in ciftbx.sys, which include the same common declarations as are found in ciftbx.cmn and additional declarations used internally within CIFtbx, are provided for use in maintaining the library. Caution is needed in making internal modifications to the library to maintain the desired relationships among the actions of various routines and the states of variables declared in the common blocks.
Statements are written in the first 72 columns of a line, reserving columns one through five for statement labels and using column six for continuation. Approaches that would require the use of C libraries or non-portable Fortran extensions are avoided. For this reason, all the internal service routines are written in Fortran, all memory needed is preallocated with DIMENSION statements and a direct-access file is used to hold the working copy of a CIF.
