setDec and forbidden interval/decoration combinations

[Vincent Lefevre <vincent@xxxxxxxxxx>]

The current draft (8.1, 2013-10-25) says in §11.5.2:

  Given an interval x and a decoration dx, the operation setDec(x, dx)
  returns the decorated interval x_dx if this is an allowed combination.
  The cases of forbidden combinations are as follows:
  - setDec(Empty, dx) where dx is one of def, dac or com returns NaI.
  - setDec(x, com), for any unbounded x, returns Entire_dac.
  - setDec(x, ill) for any x, whether empty or not, returns NaI.

I think that the 3rd item is obvious. But the first two items do not
seem to be consistent. I would have chosen either:

  - setDec(Empty, dx) where dx is one of def, dac or com returns NaI.
  - setDec(x, com), for any unbounded x, returns NaI.

so that any forbidden combination gives NaI, or

  - setDec(Empty, dx) where dx is one of def, dac or com returns Empty_trv.
  - setDec(x, com), for any unbounded x, returns Entire_dac.

to set the decoration to the maximum allowed one in both cases.

Any comment?

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Vincent Lefèvre <vincent@xxxxxxxxxx> - Web: <http://www.vinc17.net/>
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