Re: Possible bug in Table and/or lists (Mathematica v.7)
- To: mathgroup at smc.vnet.net
- Subject: [mg108129] Re: Possible bug in Table and/or lists (Mathematica v.7)
- From: dh <dh at metrohm.com>
- Date: Tue, 9 Mar 2010 06:19:57 -0500 (EST)
- References: <hmvqbb$1as$1@smc.vnet.net>
Hi Vijay,
this has to do with list assignment. If on both side of "=" we have list
of the same length, the assignment is element by element. If the length
differ, the right list is assigned to every element on the left side. A
workaround is to use "Sequence"E.g. try:
t[[{1, 2, 3}]] = {q, q, q};
t[[{1, 2, 3}]] = Sequence@{q, q, q};
Daniel
On 07.03.2010 10:06, Vijay Kaul wrote:
> I found this potential bug in Mathematica 7, running on Win XP and OS
> X and it's easily reproducible.
>
> If I try the following:
>
> dim = 3;
> t = Table[1, {2*dim}, {2*dim}];
> t // Grid
> t[[-dim ;;]] = Table[1, {dim}];
> t // Grid
>
> I get unexpected results: the last three rows, rather than being each
> a three element list, are, instead, single "1"s. On the other hand
>
> dim = 3;
> t = Table[1, {2*dim}, {2*dim}];
> t // Grid
> t[[-dim ;;]] = Table[1, {dim + 1}];
> t // Grid
>
> works as expected.
>
> In general, dimensions where the shorter lists are *not* half the
> larger dimension seem to work just fine. I can also reproduce the
> problem by creating a list of length 2N and then trying to fill half
> of it with lists of length 2N and half with lists of length N.
>
> Maybe I'm missing something, but it baffled me and some others who
> looked at it.
>
> Also, I'm not sure where or how to find a Mathematica bug-list, and I
> didn't see a FAQ around here, but I'm relatively unexposed to usenet,
> newsgroups, and Google groups, so I may have missed some obvious
> stuff.
>
> So, with thanks and/or apologies in advance,
> -Vijay
>
--
Daniel Huber
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