Timeline for How does Mathematica decide that Log[2,8] is integer?
Current License: CC BY-SA 3.0
14 events
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| Feb 3, 2013 at 20:19 | vote | accept | stevenvh | ||
| Oct 18, 2012 at 9:53 | comment | added | J. M.'s missing motivation♦ | Yes, that too. :) | |
| Oct 18, 2012 at 9:51 | comment | added | Mr.Wizard |
@J.M. ah... or BitLength[n] != BitLength[n-1]?
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| Oct 18, 2012 at 9:49 | comment | added | J. M.'s missing motivation♦ |
I was thinking of a test along the lines of n == 2^(BitLength[n] - 1)
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| Oct 18, 2012 at 9:47 | comment | added | Mr.Wizard |
@J.M. please pardon my lack of understanding, but how do you figure that? Isn't it rather like Floor@Log2@x?
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| Oct 18, 2012 at 9:41 | comment | added | J. M.'s missing motivation♦ |
"what are you thinking?" - well, BitLength[] is effectively equivalent to Log2[], so...
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| Oct 18, 2012 at 8:54 | comment | added | Mr.Wizard |
@stevenvh I don't think your question has been answered but I'm not sure it can be by anyone other than the Mathematica developers. Nevertheless given the vastly superior performance of BitAnd it apparently isn't anything special. :^)
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| Oct 18, 2012 at 8:51 | comment | added | stevenvh |
Aaah, I should have dug deeper in the documentation :-(. I knew about Log10[], but didn't know there was a Log2[] as well. Thanks. (No need for Taylor here)
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| Oct 18, 2012 at 8:49 | history | edited | Mr.Wizard | CC BY-SA 3.0 |
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| Oct 18, 2012 at 8:43 | comment | added | Mr.Wizard | @J.M. what are you thinking? | |
| Oct 18, 2012 at 8:39 | comment | added | J. M.'s missing motivation♦ |
If one still wants to take the logarithm route, BitLength[] is one function to look at...
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| Oct 18, 2012 at 8:34 | history | edited | Mr.Wizard | CC BY-SA 3.0 |
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| Oct 18, 2012 at 8:23 | history | edited | Mr.Wizard | CC BY-SA 3.0 |
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| Oct 18, 2012 at 8:12 | history | answered | Mr.Wizard | CC BY-SA 3.0 |