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>>>>> On Tue, 30 May 2017, Alexis Ballier wrote: |
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> The way I see it, this boils down to spec'ing something that |
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> guarantees there's a unique solution given an input. The solution |
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> does not have to be good or bad (we don't have a good metric on that |
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> anyway), it just has to be deterministic so that developers can |
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> arrange their REQUIRED_USE constraints to have PM chose the proper |
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> solution. |
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Right. As I see it, the problem we must solve is that for k USE flags |
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there are 2**k possible combinations, but there may be only n |
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combinations that are valid, with n < 2**k. For example, for |
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IUSE="foo bar baz" there are 2**3 = 8 possible combinations, but with |
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REQUIRED_USE="|| ( foo bar baz )" or "^^ ( foo bar baz )" only 7 or 3 |
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of them are valid, respectively. |
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Now we can either just specify which of the combinations are valid; |
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this is what REQUIRED_USE currently does. Or we can specify a complete |
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mapping from every invalid input combination of flags to a valid |
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output combination. I think we should do the latter. |
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Ulrich |
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