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Talk:Truncatable primes: Difference between revisions
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:::Hi Gerard, I still can't see how talking about taking a digit would mean anything but a decimal digit from a base-10 representation of a prime? The task description on RC leaves out any mention of numerical bases. You introduce bases above when you talk of the number of right-truncatable primes but if you had just said that "There are only 83 right-truncatable primes" then wouldn't a base of 10 be automatically inferred? --[[User:Paddy3118|Paddy3118]] 21:48, 12 September 2012 (UTC)
:::: No, as others have discussed this (outside of Rosetta Code) and are careful in mentioning what base is being meant
<br> If you take the digit '''4''' (from the 1423 number) ...
<br><br>this statement doesn't infer that 1423 is base ten. -- [[User:Gerard Schildberger|Gerard Schildberger]] 23:05, 12 September 2012 (UTC)
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There are a few number sequences that are in (or implied) base ten (but some sequences could be in other bases):
* look-and-say (look, then say how many digits there are, in order, of a positive integer)
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* rep unit primes (primes which only contain the digit one)
(Pardon me if some of those sequences should be capitalized.) Also pardon me if I didn't get the exact definition stated correctly, I was trying to be succinct so that the definition would fit on one line. I was switching between digits and numerals, numbers and integers, and whatnot. I took a couple of handfuls of sequences that can be described easily (well, I tried to keep the descriptions short and simple).
<br>A few sequences are shown in base ten, but use another base, such as xenodrome numbers (base 12), xenodrome numbers are integers, which expressed in base 12, has every numeral (digit) different from each other, that is, each digit is unique). -- [[User:Gerard Schildberger|Gerard Schildberger]] 22:46, 12 September 2012 (UTC)
<br><br>I've written a handy-dandy, slicer-dicer, one-size-fits-all, all-in-one general purpose calculator (in REXX) that has all those functions and more, around 1,500 functions). A lot of the Rosetta Code tasks that have REXX solutions were ripped out of that program, dumbed down, much (if not all) error checking removed, and generally, put on a severe diet before posting to RC. I wish Rosetta Code had the space for it. -- [[User:Gerard Schildberger|Gerard Schildberger]] 23:05, 12 September 2012 (UTC)
:Hi again Gerard, my point wasn't that truncatable primes could not be done in other bases, just that, in the lack of any base mentioned in the task description then a base of ten is meant and has been understood by all the example writers for this task (including yourself). Mentioning base 10 as I have now done might not help someone new to the concept and might distract them from what is needed to understand the task. Do you think mentioning base 10 is ''necessary''?
:Maybe because you have or are considering a solution in other bases, this is driving your request? I am questioning it as I would like to understand if I have dumbed the task down too much and truly missed a salient point or if not mentioning the base was enough and maybe more clear for the purposes of the task (not involving bases other than ten). I wish others would add their opinions too :-)<br>--[[User:Paddy3118|Paddy3118]] 06:54, 13 September 2012 (UTC)
::Paddy, be careful what you wish for. The largest truncatable prime in a given base can be estimated by probabalistic methods from the Zeta Function. Computing the largest truncatable prime in several bases and comparing them with the estimated values can be used to gain insight into the Zeta Function and maybe the Reimann Hypothosis.--[[User:Nigel Galloway|Nigel Galloway]] 12:01, 14 September 2012 (UTC)
::While claryfing this task you may wish to be clear if you consider 1 to be a prime number, you should not. From which it follows that 13 is a left reducable prime, but not a right reducable prime.--[[User:Nigel Galloway|Nigel Galloway]] 12:10, 14 September 2012 (UTC)
:::Surely treating one as prime is not the ''[http://oeis.org/A000040 normal]'' thing to do. Both Sloane and Mathworld don't consider it so. If someone ios mentioning Truncatable primes in bases other than ten then what base you are considering is important. You may well be having conversations off-site that are clarified if the bases involved are stated, but the task description is right in itself. --[[User:Paddy3118|Paddy3118]] 17:36, 14 September 2012 (UTC)
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