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On sob, 2017-06-10 at 00:30 +0200, Michał Górny wrote: |
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> Below I have listed the clauses I'd like to ban in a few logical groups, |
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> along with explanations and examples. |
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> |
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> [...] |
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Actually, after some thinking, here's one more: |
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4. All-of operator inside || |
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---------------------------- |
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While this is not as bad as the others, it probably makes sense to ban |
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it to preserve symmetry between operators. It has very little real use, |
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killing it simplifies all algorithms even more. Since it was the last |
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valid use of all-of operator, this means we can ban it altogether |
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in REQUIRED_USE. |
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|
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The only real use in ::gentoo right now is: |
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|
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|| ( deprecated ( gtk3 introspection ) ) ) |
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which is equivalent to: |
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!gtk3? ( deprecated ) !introspection? ( deprecated ) |
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While the former is a little shorter and might be considered somewhat |
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readable, I don't think it's worth to keep the extra complexity for |
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a single package. Especially considering that the package is not even |
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using it correctly since -- judging by the code -- it should actually |
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have: |
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|
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python? ( gtk3? ( introspection ) ) |
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which would render the above clause irrelevant. |
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The two remaining uses of all-of in ::gentoo are obvious mistakes -- |
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accidental extra parentheses. |
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|
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> Resulting AST |
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> ============= |
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> |
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> If all three classes I've mentioned were banned, the AST would look |
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> like: |
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> |
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> REQUIRED_USE := [<top-expr>...] |
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> |
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> top-expr := <flag> | <use-cond> | <any-of> | <most-one-of> | <exactly-one-of> |
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> |
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> flag := ['!']<flag-name> |
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> |
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> use-cond := ['!']<flag-name>'? (' <top-expr>... ')' |
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> |
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> any-of := '|| (' <any-of-expr>... ')' |
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|
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Now: |
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|
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any-of := '|| (' <flag>... ')' |
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> any-of-expr := <flag> | <all-of> |
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|
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Scratch that. |
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> most-one-of := '??' ( <flag>... ) |
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> |
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> exactly-one-of := '^^' ( <flag>... ) |
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> |
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> all-of := '(' <flag>... ')' |
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> |
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> |
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> Note that only USE conditionals are deeply nested now. Of all other |
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> groups, || can contain pure flags and/or all-of blocks (which contain |
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> only pure flags), and ?? and ^^ contain pure flags only. |
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> |
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Now even better. ||, ?? and ^^ all are pure, flat groups of USE flags. |
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-- |
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Best regards, |
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Michał Górny |
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