XA Report, Approach "Difficulties"

Approach

Difficulties

Unfortunately the previous idea of modular programming lead to some difficulties. For some features it was not possible to write independent procedures, because of the following reasons:

For drawing the graphs XA uses the SciPlot widget by Alan Richardson and Robert W. McMullen. SciPlot returns an identity number for each graph which will be necessary if the values or resources of a plot have to be changed. Therefore a global variable is necessary to keep this identity number after the drawing procedure has been called.
Unfortunately it is not possible to change the argument list of Motif callback functions. Therefore it was unavoidable to use some global variables to pass additional parameters.
During the implementation phase of XA I had some difficulties with segmentation faults and core dumps because of various pointer errors. Therefore I decided to remove or simplify some features which were previously independent. For example, the global variable for a atom is directly modified when the internal atom data structure is changed.

In the online documentation these problems are mentioned with every procedure where they might affect further developments. Additionally, the global variables are mentioned on which the execution is based on.

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