in reply to sorting and grouping by

You haven't defined what you mean by sorting, or grouping. You haven't explained what -> means relative to set theory. Your definition of what comprises a set is inconsistant. (A is empty?)

Could you provide a little more detail please?

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Re^2: sorting and grouping by
by apl (Monsignor) on Mar 13, 2008 at 10:05 UTC
    First, in my defense, it looks like Joost had some confusion about what you meant as well.

    Second, A intersects B at 22, while B intersects C at ( 22 .. 33 ), and wholly contains D. The statement

    B contains the set of B->{C, D}, C->{D}, A->{} etc.
    seems to differentiate '->' from 'contains', as well as using two different ways of defining a set ( '{}', and 'the set').

    In any event, I'm glad you got the help you needed.

Re^2: sorting and grouping by
by ikegami (Patriarch) on Mar 13, 2008 at 02:30 UTC
    -> seems to mean "has for subsets", since B->{C, D} seems to mean "C" and "D" are wholly contained in "B".
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