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- - **EnumSet, what the ?**
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EnumSet, what the ?I discovered that only the static members of EnumSet are public.
In other words, EnumSets appear to be immutable at least to anyone but Sun. This is highly puzzling. Why bother with a bitset representation for a set without any mathematical set operations? There is complement, but where are union (or), intersection (and), set difference (xor), bitwise operations? Equals at first looks to be but they defined it as object identity not bit map identity. The general purpose "of" method works mostly with enum constant operands, not with entire EnumSets. Perhaps I should simply rewrite EnumSet. -- Bush crime family lost/embezzled $3 trillion from Pentagon. Complicit Bush-friendly media keeps mum. Rumsfeld confesses on video. http://www.infowars.com/articles/us/...s_rumsfeld.htm Canadian Mind Products, Roedy Green. See http://mindprod.com/iraq.html photos of Bush's war crimes |

Re: EnumSet, what the ?"Roedy Green" <look-on@mindprod.com.invalid> wrote in message news:op0sc1d3i55u9eath8l3404rldnvfndmr8@4ax.com... >I discovered that only the static members of EnumSet are public. > > In other words, EnumSets appear to be immutable at least to anyone > but Sun. > > This is highly puzzling. Why bother with a bitset representation for a > set without any mathematical set operations? There is complement, but > where are union (or), intersection (and), set difference (xor), > bitwise operations? Equals at first looks to be but they defined it > as object identity not bit map identity. Have you looked at EnumSets' super classes, AbstractSet and AbstractCollection? Maybe their bulk operations will give you what you want. For example, AbstractSet overrides the equals in Object so that it gives you true set equality, not object equality. George W. Cherry > The general purpose "of" method works mostly with enum constant > operands, not with entire EnumSets. > > Perhaps I should simply rewrite EnumSet. > > > -- > Bush crime family lost/embezzled $3 trillion from Pentagon. > Complicit Bush-friendly media keeps mum. Rumsfeld confesses on video. > http://www.infowars.com/articles/us/...s_rumsfeld.htm > > Canadian Mind Products, Roedy Green. > See http://mindprod.com/iraq.html photos of Bush's war crimes |

Re: EnumSet, what the ?On Fri, 08 Jul 2005 04:48:23 GMT, Roedy Green
<look-on@mindprod.com.invalid> wrote or quoted : >Perhaps I should simply rewrite EnumSet. I discovered another peculiar feature of RegularEnumSet look at this code: void addRange(E from, E to) { elements = (-1L >>> (from.ordinal() - to.ordinal() - 1)) << from.ordinal(); } He is constructing a bit mask of ones for the range, 1=included, 0=excluded, 0=unused, counting bits from the lsb. e.g. binary 000111111100 for ordinals 2 through 8. Then instead of doing elements |= for addRange he does elements = which really should have been called setRange. Growl! -- Bush crime family lost/embezzled $3 trillion from Pentagon. Complicit Bush-friendly media keeps mum. Rumsfeld confesses on video. http://www.infowars.com/articles/us/...s_rumsfeld.htm Canadian Mind Products, Roedy Green. See http://mindprod.com/iraq.html photos of Bush's war crimes |

Re: EnumSet, what the ?Roedy Green <look-on@mindprod.com.invalid> wrote in message news:<op0sc1d3i55u9eath8l3404rldnvfndmr8@4ax.com>. ..
> I discovered that only the static members of EnumSet are public. > > In other words, EnumSets appear to be immutable at least to anyone > but Sun. EnumSet is not immutable, it implements the mutating methods in the Set interface. > This is highly puzzling. Why bother with a bitset representation for a > set without any mathematical set operations? There is complement, but > where are union (or), intersection (and), set difference (xor), > bitwise operations? Equals at first looks to be but they defined it > as object identity not bit map identity. An EnumSet is not a bitset, so it shouldn't contain any bit operations and correctly doesn't. Sun has chosen to internally represent the set as a bitset, but that's another issue. The EnumSet implements all methods in the Set interface, so union == addAll(), intersection == retainAll(), difference == a combination of retainAll(), addAll() and removeAll(). /JN |

Re: EnumSet, what the ?"Jesper Nordenberg" <megagurka@yahoo.com> wrote in message news:9c838fb.0507080259.11017943@posting.google.co m... > Roedy Green <look-on@mindprod.com.invalid> wrote in message > news:<op0sc1d3i55u9eath8l3404rldnvfndmr8@4ax.com>. .. >> I discovered that only the static members of EnumSet are public. >> >> In other words, EnumSets appear to be immutable at least to anyone >> but Sun. > > EnumSet is not immutable, it implements the mutating methods in the > Set interface. > >> This is highly puzzling. Why bother with a bitset representation for a >> set without any mathematical set operations? There is complement, but >> where are union (or), intersection (and), set difference (xor), >> bitwise operations? Equals at first looks to be but they defined it >> as object identity not bit map identity. > > An EnumSet is not a bitset, so it shouldn't contain any bit operations > and correctly doesn't. Sun has chosen to internally represent the set > as a bitset, but that's another issue. The EnumSet implements all > methods in the Set interface, so union == addAll(), intersection == > retainAll(), difference == a combination of retainAll(), addAll() and > removeAll(). Yes, I said something similar (but not so well) in an earlier post to Roedy. Hey Roedy, Java's a high-level language; get your mind out of the bit gutter. : o ) George |

Re: EnumSet, what the ?On Fri, 8 Jul 2005 14:16:46 -0400, "George Cherry"
<GWCherryHatesGreenEggsAndSpam@alum.mit.edu> wrote or quoted : >Yes, I said something similar (but not so well) >in an earlier post to Roedy. Hey Roedy, Java's >a high-level language; get your mind out of the >bit gutter. : o ) my background is math. I expect operations like union, intersection, on something that calls itself a set, which map very nicely to what an assembler programmer like me does with bitmaps. It turns out the interesting methods of an EnumSet are way down in the AbstractSet class. There seems to be a heck of a lot of dithering compared with the way I implemented such a feature in Abundance. -- Bush crime family lost/embezzled $3 trillion from Pentagon. Complicit Bush-friendly media keeps mum. Rumsfeld confesses on video. http://www.infowars.com/articles/us/...s_rumsfeld.htm Canadian Mind Products, Roedy Green. See http://mindprod.com/iraq.html photos of Bush's war crimes |

Re: EnumSet, what the ?"Roedy Green" <look-on@mindprod.com.invalid> wrote in message news:on3vc1dd9fjsidkdjmbv005gdq25gj6d11@4ax.com... > On Fri, 8 Jul 2005 14:16:46 -0400, "George Cherry" > <GWCherryHatesGreenEggsAndSpam@alum.mit.edu> wrote or quoted : > >>Yes, I said something similar (but not so well) >>in an earlier post to Roedy. Hey Roedy, Java's >>a high-level language; get your mind out of the >>bit gutter. : o ) > > my background is math. I expect operations like union, intersection, > on something that calls itself a set, which map very nicely to what an > assembler programmer like me does with bitmaps. It turns out the > interesting methods of an EnumSet are way down in the AbstractSet > class. Okay, but Joshua Bloch's elegant Collections Framework gives you all the set operations--and they work between different Set implementations (including EnumSet) very conveniently. EnumSet implements the Collections Framework's root interface, Collection, and, of course, its subinterface, Set. It turns out that EnumSet's relevant bulk operations are way up in the Collection interface, and they are defined explicitly as set operations in the API for the Set interface. (Are interfaces neat or what?) Bloch's excellent tutorial on the Java Collections Framework is at http://java.sun.com/docs/books/tutorial/collections/ The following is from the tutorial The bulk operations are particularly well suited to Sets; when applied to sets, they perform standard set-algebraic operations. Suppose s1 and s2 are Sets. Here's what the bulk operations do: a.. s1.containsAll(s2): Returns true if s2 is a subset of s1. (s2 is a subset of s1 if set s1 contains all the elements in s2.) b.. s1.addAll(s2): Transforms s1 into the union of s1 and s2. (The union of two sets is the set containing all the elements contained in either set.) c.. s1.retainAll(s2): Transforms s1 into the intersection of s1 and s2. (The intersection of two sets is the set containing only the elements that are common to both sets.) d.. s1.removeAll(s2): Transforms s1 into the (asymmetric) set difference of s1 and s2. (For example, the set difference of s1 - s2 is the set containing all the elements found in s1 but not in s2.) > There seems to be a heck of a lot of dithering compared with the way I > implemented such a feature in Abundance. Fooling around directly with bits is a heck of a lot of dithering compared with the way Bloch specified and implemented set operations in the Java Collections Framework--and you still get the efficiency of bit vector dithering, because the implementation of EnumSet uses bit vectors behind the high level scene. George W. Cherry |

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