On Thu, 19 Mar 2009 14:26:53 -0500, Patrick O'Keefe wrote: >> >>The description in the manual is correct; describing it with >>the less specific term "default" might lead the programmer to >>expect the program to say "something" rather than "X.7", or >>at least to be uncertain. >>... > >I agree, but I think the astonishment is aimed at the drop rather >than the stem assignment. (At least MY astonishment is.) That >behavior implies that the interpreter has to maintain both a list >of specifically assigned variables and a list of specifically dropped >variables (at least for stems that have been assigned). I have no >idea how the interpreters actually support the behavior of stem >initialization, but I'm quite sure they don't predefine and assign >every possible variable for the given stem. They must, in fact, >treat the assigned value as a default to be used for each >unassigned and undropped variable associated with the stem. > >Including dropped variables in that behavior just adds work for the >interpreter. > >Collishaw books include a sample of this behavior so there is no >doubt he intended the language to work this way, but I am still >astonished. > You have a pretty good description of how the misunderstanding arises: journeyperson programmers attempt to infer an mechanism of implementation, then erroneously assume the developers take shortcuts because it's too complicated to do it right.
I confess I often do the same. But then I test. Sometimes I'm plesantly surprised to find the implementation meets the specification. Other times, I find that the implementor took the shortcut, and I submit a PMR. This thoroughly annoys the support people who argue that I should expect that it would be implemented in the simple and obvious way, not as specified. I may not be able to do that much longer. -- gil ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
