Hello again,

Further to the recommendation by oswin krause for trying out vector_indirect, I would like to ask the following.

The documentation (http://www.boost.org/doc/libs/1_53_0/libs/numeric/ublas/doc/html/classboost_1_1numeric_1_1ublas_1_1vector__indirect.html#_details) states that a vector_indirect can be constructed by a broad range of vectors of indices, such as

std::vector, ublas::vector or indirect_array.

The problem is I seem to be able to construct an indirect vector using indirect_array types _only_. When for example I use a ublas::vector<size_t> or a std::vector<size_t> as a vector of indices I get a compilation error from gcc 4.7.2 that there is a preprocess member missing.

Is the documentation simply out of date and only the use of indirect_arrays is allowed, or is it a bug? Thanks in advance.

Regards,

Giorgos

Message: 1
Date: Mon, 20 May 2013 17:49:30 +0100 (BST)
From: gsermaid <linuxfever@yahoo.gr>
To: "ublas@lists.boost.org" <ublas@lists.boost.org>
Subject: [ublas] Support for more general ranges
Message-ID:
??? <1369068570.74879.YahooMailNeo@web172106.mail.ir2.yahoo.com>
Content-Type: text/plain; charset="iso-8859-1"

Hi all,

I would like to ask if there is any way to create a vector proxy based on a general range of indices. For example, if I have
a vector

vector<unsigned> x(4);
x <<= 1,2,3,4;

and a vector of indices?

vector<size_t> k(2);
k <<= 0,3;

I would like to be able to create a vector proxy as follows

vector_proxy<unsigned> mysubvector(x, k);

with the property that

mysubvector[i] = x[k[i]].

I know I can create a simple new class which provides this functionality but ideally I also want to have
all the useful iterator functionality and mathematical operations supported by a typical ublas vector. Is this currently supported? If not, is there an easy way to?
implement it and have all the functionality that ublas offer? Finally, do you think something like this could be included in future versions?

Regards,
Giorgos
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Message: 2
Date: 20 May 2013 18:51:54 +0200
From: "oswin krause" <oswin.krause@ruhr-uni-bochum.de>
To: ublas@lists.boost.org
Subject: Re: [ublas] Support for more general ranges
Message-ID: <519A54AA.9020907@ruhr-uni-bochum.de>
Content-Type: text/plain; charset="iso-8859-1"; Format="flowed"

Hi,

take a look at vector_indirect.

On 20.05.2013 18:49, gsermaid wrote:
> Hi all,
>
> I would like to ask if there is any way to create a vector proxy based
> on a general range of indices. For example, if I have
> a vector
>
> vector<unsigned> x(4);
> x <<= 1,2,3,4;
>
> and a vector of indices
>
> vector<size_t> k(2);
> k <<= 0,3;
>
> I would like to be able to create a vector proxy as follows
>
> vector_proxy<unsigned> mysubvector(x, k);
>
> with the property that
>
> mysubvector[i] = x[k[i]].
>
> I know I can create a simple new class which provides this
> functionality but ideally I also want to have
> all the useful iterator functionality and mathematical operations
> supported by a typical ublas vector. Is this currently supported? If
> not, is there an easy way to
> implement it and have all the functionality that ublas offer? Finally,
> do you think something like this could be included in future versions?
>
> Regards,
> Giorgos
>
>
> _______________________________________________
> ublas mailing list
> ublas@lists.boost.org
> http://lists.boost.org/mailman/listinfo.cgi/ublas
> Sent to: Oswin.Krause@ruhr-uni-bochum.de

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