Slashdot Mirror


User: maxwell+demon

maxwell+demon's activity in the archive.

Stories
0
Comments
12,279
First seen
Last seen
Profile
(view on slashdot.org)

Comments · 12,279

  1. Re:No Changes! on Designer on Slashdot Overhaul Plans · · Score: 1

    One possibility would be to allow selection of different skins from the user preferences, like Wikipedia does.

  2. A small nit which made me wonder on Designer on Slashdot Overhaul Plans · · Score: 1

    In normal reading, every non-top comment has two links: parent, and reply. This makes sense.
    When you click reply, the comment is shown again above the input textbox, which still makes sense.
    Below the comment, there's one link. And this link says: reply.
    Now why should I want to use the reply link, when my reply form is already right before my nose?
    Noreover, why remove the link to parent (which, unlike the reply link, I actually would use from time to time)?

    Not that it's a big problem, not clicking a pointless link is more than easy, and if I want to get to the parent, it's just one extra mouse click (once on the comment number to get a normal display of the message, where I then have the parent link). It's just that it looks stupid to me every time again to see a pointless reply link on the reply page, while obviously the coders have done some work to remove the (actually useful) parent link.

  3. Re:Aluminium Reality or Aluminum Realty? on Transparent Aluminum a Reality · · Score: 1
    Then there's Helum, that noble gas.

    I prefer Platinium, the noble metal :-)
  4. Re:transparent oxide-nitride, not a metal on Transparent Aluminum a Reality · · Score: 1
    Are we going to suddenly see completely transparent vehicles driving around?

    I doubt it. After all, you probably don't want the enemy seeing all the actions you do in the vehicle ("Oh, they are loading the weapon now, maybe this would be a good time to attack ...")
  5. Re:Not too big a deal on Mozilla Firefox 1.0.7 DoS Exploit · · Score: 3, Funny
    I reported some DOS bugs against firefox

    I didn't know there's a DOS port of Firefox. :-)
  6. Re:Cool... BUT (there's always a BUT) on Nokia Engineers on KHTML · · Score: 2, Funny
    4. Can I still make phone calls of this phone? :)

    You'll make kphone kalls instead.
  7. Re:Sticky Triangles on Your Favorite Math/Logic Riddles? · · Score: 1

    Easy: I remember from math that a line is a degenerated triangle. Then I note that each stick already represents a line. Therefore I don't have to do anything to get six (degenerated) triangles.

  8. Re:Divisible by 3 or 6? on Your Favorite Math/Logic Riddles? · · Score: 1

    Rule for n:
    Multiply the digit representing 10^k by (10-n)^k, and add the results together. The resulting number is a multiple of n exactly if the original number was. Instead of (10-n)^k of course any number which differs from that by a multiple of n can be used. (The proof and the generalization for bases other than 10 is left as exercise to the reader :-))

    Examples:
    n = 2:
    Pure rule:
    * 124 -> 1*64 + 2*8 + 4 = 12. 12 is a multiple of 2, therefore 124 is, too.
    * 123 -> 1*64 + 2*8 + 2 = 11. 11 is not a multiple of 2, therefore 123 isn't either.
    Improved rule:
    Since 8^n is a multiple of 2 for n>=1, it can be subtracted from itself, giving 0. Since 0 times anything is 0, this way only the last digit remains, and we get the well-known rule that a number is even exactly if the last digit is even.

    n=3:
    Pure rule:
    * 123 -> 1*49 + 2*7 + 3 = 66. 66 is a multiple of 3, therefore 123 is, too.
    * 124 -> 1*49 + 2*7 + 4 = 67. 67 is not a multiple of 3, therefore 124 isn't either.
    Improved rule:
    7 is 2*3+1, therefore 7^k = (2*3+1)^k = sum_i binomial(k,i) 2^i*3^i. All summands except for i=0 are multiples of 3 and can therefore be eliminated. The summand for i=0 is just 1. Therefore we get the well known rule that a number is a multiple of 3 exactly if the sum of it's digits is.
    Note that there is not really the need to carry out the general calculation, you can do it step by step: Since 7 can be replaced with 1, 7*7 can be replaced with 7*1, which again is 7 and can be replaced by 1. That is, you always can multiply the "reduced" number instead of the original one for determining the next "reduced power". I'll do this in my following examples.

    n=4:
    Pure rule:
    124 -> 1*36 + 2*6 + 4 = 52. 52 is a multiple of 4, therefore 124 is, too.
    Improved rule:
    6-4 = 2, therefore the next-to-last digit can be multiplied by 2 instead of 6. For n>=2, 6^n is a multiple of 4 and therefore can be reduced to 0 (alternatively: for the third-last daigit, 6*2=12, 6*2-3*4=0, and 0*6 = 0 for all other digits). Therefore you need only look at the last two digits, and the number is multiple of 4 exactly if 2*(next-to-last digit)+(last digit) is.

    In the following examples, I'll directly skip to the improved rule.

    n=5:
    Since 10-5 is 5, again only the last digit matters.

    n=6:
    1*4 = 4
    4*4 = 16, 16-2*6 = 4
    Therefore all digits but the first have to be multiplied by 4, and then all of them added together.
    Example:
    1296 -> 4*1 + 4*2 + 4*9 + 6 = 54 = 6*9.
    In practice, it's probably simpler to remember that a number is a multiple of 6 exactly if it is both a multiple of 2 and a multiple of 3, and test those two separably.

    n=7:
    Now we come to the first interesting case (i.e. the first one which gives a non-trivial rule). Consecutive multiplication with 3 and eliminating multiples of 7 gives the series:
    1, 3, 9-7=2, 6, 18-14=4, 12-7=5, 15-14=1, ...
    You see, it's a cycle of 6 numbers. Let's see the rule in action, with a sufficiently large number:
    Is 14663586 a multiple of 7? Well, let's see:
    6*1 = 6
    8*3 = 24
    5*2 = 10
    3*6 = 18
    6*4 = 24
    6*5 = 30
    4*1 = 4
    1*3 = 3
    --------
    sum = 119
    Now, it's not hard to check that 119 = 70+49 is a multiple of 7. Otherwise, we could just do a second iteration:
    9*1 = 9
    1*3 = 3
    1*2 = 2
    --------
    sum = 14
    Ok, now it's obvious, isn't it?

    Now you mentioned 11. So 10-11 = -1, therefore you have to multiply the digits with (-1)^k, i.e. subtract the sum of the even-position digits from the sum of the odd-position ones. Alternatively, you can of course alter by 11 to get a positive result (which in this case is 10 again), and then for the next step you get 10*(-1) = -10, which then gets altered to 1 again. Which means an alternate rule is to split the number in groups of two digits and sum them up.
    Let's try both rules on 1051138:
    Alternation rule: 1-0+5-1+1-3+8 = 11, which clearly is a multiple of 11-
    Digit-pair rule: 1+05+11+38 = 55, also obviously a multiple of 11.

  9. Re:SEND + MORE = MONEY on Your Favorite Math/Logic Riddles? · · Score: 1

    You want to maximize the money.

  10. Re:Fork in the road on Your Favorite Math/Logic Riddles? · · Score: 1

    Indeed I'd expect both to come from the Village of Life, because if they were from the Village of Death, they certainly would be dead!

  11. Re:Fork in the road on Your Favorite Math/Logic Riddles? · · Score: 1

    Which the liar will probably answer with the direction you came from :-)

  12. Re:Fork in the road on Your Favorite Math/Logic Riddles? · · Score: 1

    And of course the truth-teller could say: "I don't know. Otherwise I'd already be there, instead of standing here and thinking about what to do."

  13. Re:Light Bulb on Your Favorite Math/Logic Riddles? · · Score: 1

    What if the light bulb doesn't work?
    But since there was no requirement that additional tools may not be used, there's of course a simple solution:
    Step 1: Go into the room and connect a voltmeter to the light bulb. Connect that voltmeter to a sender which sends you the result out of the room. There's no need to enter the room again now.
    Step 2: Try all the switches and watch the voltage.

  14. Re:That's Irrevellant on Cross-Site Scripting Worm Floods MySpace · · Score: 1
    One of the problems he exploited was that IE obviously eliminates newline characters before searching for the tags. That is, if you write
    "Javas
    cript"

    inside an attribute, then IE will interpret that as "Javascript" anyway, but it evaded the filter at MySpace (which did scan for "Javascript"). Now I'm not sure that it's really the website's fault not to know about an IE bug which is that stupid.
  15. Re:Quick and Dirty solution on Cross-Site Scripting Worm Floods MySpace · · Score: 1

    Well, just remove the "++i", and you can also remove the "almost" part of your description.
    If you find a corresponding browser vulnerability, you just might switch off JavaScript with your JavaScript code, of course :-)

  16. Re:Aww... on Cross-Site Scripting Worm Floods MySpace · · Score: 4, Insightful

    Well, having over 1 million foes is also an achievement ...

  17. Re:where would be linux? on 20th Anniversary of Windows · · Score: 2, Insightful

    I'm sure it would be there, and it basically would be Linux. It just wouldn't compete with Windows, but maybe with an OS based on GEM (remember, originally Windows also just was a GUI on top of DOS), or with MacOS, or maybe with some OS which doesn't even exist in our world but would have been written if Windows had not existed.

  18. Re:FWIW on 20th Anniversary of Windows · · Score: 1

    Microsoft made computing cheap? So Microsoft created all those IBM PC clones which were in competition to IBM's own products and therefore forced the prices down?

    The reason why computers got cheap wasn't Microsoft. It was IBM building a PC from standard parts without making exclusivity deals on any vital component, thus opening up the market for PC clones (something they most certainly didn't intend :-)). Another important factor IMHO was IBM demanding a second source for the 8086/8088 (AMD), which also caused competition on that front and therefore kept the processor price down.

    And are you really sure if MS would have had relatively low DOS prices if there had been no competition (DR DOS)?

  19. Re:What's changed? on 20th Anniversary of Windows · · Score: 5, Funny

    20 years ago, you could safely ignore it.

  20. Re:Advanced CD distribution system? on Google Wants a Piece of AOL? · · Score: 1

    It's a good complement to Google's Pidgeon Rank system.

  21. Re:They disproved the likeliness of this ever work on Archimedes Death Ray · · Score: 1

    That's the NSA trying to prevent widespread knowledge about the creation of Death Rays. Just imagine what happens if terrorists get to read that!

  22. Re:Wouldn't that be like... on Holding Developers Liable For Bugs · · Score: 1

    You think one week is not enough? God created the whole universe in one week! Ok, it's not exactly bug-free ... :-)

  23. Re:How about... on Settlement Good News for MotorolaV710 Owners · · Score: 5, Funny
    How about Verizon just stop crippling their customers and unlock the locked features?

    They don't just cripple the phones, they also cripple their customers? I didn't know that they are that bad ... :-)
  24. Re:So much for this on Novell's Releases Linux Usability Testing Videos · · Score: 3, Funny
    Did you know that there's recent evidence to suggest that the assumption that print media and online media differ in the effect line length has on readability?

    Parse error: Expected verb, got '?'.
  25. Re:Define basic tasks on Novell's Releases Linux Usability Testing Videos · · Score: 2, Interesting
    Task: Make a new photo tag

    First Subtask: Understand what this task actually means. Edit the EXIF data of a JPEG file? Add a symlink to the file? Or what?