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Re: LinearRecurrence syntax

  • To: mathgroup at smc.vnet.net
  • Subject: [mg115957] Re: LinearRecurrence syntax
  • From: "Sjoerd C. de Vries" <sjoerd.c.devries at gmail.com>
  • Date: Thu, 27 Jan 2011 03:41:27 -0500 (EST)
  • References: <ihoro9$hlh$1@smc.vnet.net>

Actually, the syntax you are using is not documented in the doc page's
syntax box (same is true for Ordering). The documentation only
mentions n and {nmin,nmax} as possible arguments. It seems it uses n
or {1,n} if you enter {n}. I agree that using the {n,n} interpretation
instead would be more logical. It's not pretty, but working around it
is not a big deal.

Cheers -- Sjoerd

On Jan 26, 11:07 am, "Mr. Wizard" <gl... at flashmail.com> wrote:
> It seems to me that the syntax for LinearRecurrence is not in
> agreement with other Mathematica functions.
>
> In:=  LinearRecurrence[{1, 1}, {1, 1}, {10}]
> Out= {1, 1, 2, 3, 5, 8, 13, 21, 34, 55}
>
> I expected 55 or {55}.  One must enter 10 twice:
>
> In:=  LinearRecurrence[{1, 1}, {1, 1}, {10,10}]
> Out= {55}
>
> Contrast this with:
>
> Take[Range@5, {3}]
>
> Ordering[Range@10, {5}]
>
> StringTake["abcdefg", {3}]
>
> IntegerPartitions[5, {3}]
>
> Subsets[Range@4, {3}]
>
> Permutations[Range@3, {2}]
>
> In none of these cases must one enter the index twice.
>
> Further, the functions that take a Levelspec, read {x} as the
> specific level x, not one through x.  Again, one does not have to enter=
 {x, x}.
>
> a = Array[Plus, {4, 5}];
>
> Total[a, {2}]
>
> Map[EvenQ, a, {2}]
>
> Perhaps I am overlooking something obvious, but it seems to me that
> the behavior of LinearRecurrence[list, list, {i}] should be changed
> from "one through i" to only "i."
>
> Paul



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