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Re: Processing lists of unrelated numbers with Do or While statement


On 2/2/03 at 1:13 AM, diana53xiii at earthlink.remove13.net (Diana) wrote:

>I had a problem recently where I tried to determing the PrimePi value
>of 2 times a number minus that number. This is verifying the
>Bertrand's Postulate:

>PrimePi(2x) - PrimePi(x) >=1 for all x >=2, elements of Z.

>I finally came up with: PrimePi[2*{2, 3, 5, 7, 13, 23, 43, 83, 163,
>317, 631, 1259, 2503, 4001} - {2, 3, 5, 7, 13, 23, 43, 83, 163, 317,
>631, 1259, 2503, 4001}]

>gives: {1, 2, 3, 4, 6, 9, 14, 23, 38, 66, 115, 205, 368, 551} the
>desired answer. 

Hmm... Your statement of your problem and the function agree but are not equivalent to
PrimePi[2x]-PrimePi[x].

Your function is PrimePi[2*list -list] = PrimePi[list] which is not equal to PrimePi[2*list]-PrimePi[list]

>Is there a way to process unrelated numbers with a Do
>or While or NestWhile statement? 

Clearly, the answer to your question is yes. A more specific answer depends on exactly what you mean by "process".

If process feed numbers to a function of n arguements m times then a better solution might be

MapThread[f, {list1, list2, .... listn}]


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