John Darrington <[EMAIL PROTECTED]> writes: > Great. The only problem is, that the comment at the top of the file > which says that casereaders cannot randomly seek, is no longer true.
Fixed now. > I had a look at the GUI again last night. A number of problems are > beginning to come apparent. One is the issue of inserting/deleting > cases in the middle of a casefile; I don't think it's possible. I'm > thinking of having some kind of auxiliary structure to store > inserted/deleted cases. Or perhaps casefiles can be extended to allow > us to do that? > > Another issue, is that casefiles have a fixed value_cnt, which makes > inserting/deleting variables difficult. I think the way around this > problem is to run a procedure whenever the dictionary is changed. It is possible, but nontrivial, to fix casefiles to solve both of these problems. Cases could be inserted by adding a second file and reading its data partway through the middle of the first one; some kind of index would be necessary. Deleting cases is simpler; you just arrange to ignore the ones that are deleted. If this sort of thing is taken to its logical extreme, you end up with a database system like Berkeley DB's Recno access method. Variables could be inserted by adding a second file and reading it in parallel with the first one. To delete a variable, ignore that data as you read it. How important is it to solve these problems at the casefile level? -- Ben Pfaff email: [EMAIL PROTECTED] web: http://benpfaff.org _______________________________________________ pspp-dev mailing list [email protected] http://lists.gnu.org/mailman/listinfo/pspp-dev
