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Options for Cell: Why are some of these System symbols and others not?
Recently, I was stymied when a function that I had defined in a package did not work properly. The function was designed to copy, from an open notebook, a Cell expression representing a closed cell in the notebook, and to create a new cell in the notebook, based on the closed cell, but with two Cell options modified: CellTags->"xxxx" was to be replaced by CellTags->"yyyy", and CellOpen->False was to be replaced by CellOpen->True. The change in the CellTags option worked correctly, but the change in the CellOpen option did not. After much experimentation, I discovered why: CellTags is a System symbol, but CellOpen is not -- so my package created its own CellOpen symbol in its own context. This solved my problem, but out of curiosity I then looked at the intersection (and the complement) of (i) a list of all options for Cell and (ii) a list of all System symbols. I found that, of the 144 options for Cell in Mathematica 3.0, 76 are System symbols and the other 68 are not. Does anyone know why this is? Robert Lawrence