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[array] with variable size

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Re: [Boost-users] Boost range...

Hicham Mouline

20 Nov 2008 20 Nov '08

4 p.m.

Hello, I have a third-party library that gives me a number N of doubles, then expects from me a double* to an array where it will set N elements This would have happen many times and N is variable, so I wish not to reallocate the array each time. I know however N is maxed at some value Nmax like 50. I thought of using a array that would be allocated once, then perhaps have a wrapper around it so that only N elements of it can be accessed. This seems to be a usual idiom, are there ready implementations? Regards,

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Emil Dotchevski

20 Nov 20 Nov

4:10 p.m.

On Thu, Nov 20, 2008 at 8:00 AM, Hicham Mouline wrote:

I thought of using a array that would be allocated once, then perhaps have a wrapper around it so that only N elements of it can be accessed.

This seems to be a usual idiom, are there ready implementations?

What's wrong with std::vector? You could use ::reserve to allocate memory independently of how much of it is actually being used. Emil Dotchevski Reverge Studios, Inc. http://www.revergestudios.com/reblog/index.php?n=ReCode

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Steven Watanabe

4:12 p.m.

AMDG Hicham Mouline wrote:

I have a third-party library that gives me a number N of doubles, then expects from me a double* to an array where it will set N elements

This would have happen many times and N is variable, so I wish not to reallocate the array each time.

Can't you use a vector and resize it every time? In Christ, Steven Watanabe

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Hicham Mouline

5:02 p.m.

It doesn't provide a pointer to the internal array that is required by my 3rd party lib...? while boost::array<> has c_array().... -----Original Message----- From: boost-users-bounces@lists.boost.org [mailto:boost-users-bounces@lists.boost.org] On Behalf Of Steven Watanabe Sent: 20 November 2008 16:12 To: boost-users@lists.boost.org Subject: Re: [Boost-users] [array] with variable size AMDG Hicham Mouline wrote:

I have a third-party library that gives me a number N of doubles, then expects from me a double* to an array where it will set N elements

This would have happen many times and N is variable, so I wish not to reallocate the array each time.

Can't you use a vector and resize it every time? In Christ, Steven Watanabe _______________________________________________ Boost-users mailing list Boost-users@lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users

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Steven Watanabe

5:34 p.m.

AMDG Hicham Mouline wrote:

It doesn't provide a pointer to the internal array that is required by my 3rd party lib...?

Sure it does. vector<double> v; double* pDouble = &v[0]; In Christ, Steven Watanabe

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Hicham Mouline

6:44 p.m.

Thank you, -----Original Message----- From: boost-users-bounces@lists.boost.org [mailto:boost-users-bounces@lists.boost.org] On Behalf Of Steven Watanabe Sent: 20 November 2008 17:34 To: boost-users@lists.boost.org Subject: Re: [Boost-users] [array] with variable size AMDG Hicham Mouline wrote:

It doesn't provide a pointer to the internal array that is required by my 3rd party lib...?

Sure it does. vector<double> v; double* pDouble = &v[0]; In Christ, Steven Watanabe

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Andy Tompkins

6:31 p.m.

Hi, On Thu, 20 Nov 2008 17:02:04 -0000, "Hicham Mouline" said:

It doesn't provide a pointer to the internal array that is required by my 3rd party lib...? while boost::array<> has c_array()....

Actually you can get a pointer to the internal array. void f(double *pArray); std::vector<double> v; if (!v.empty()) { f(&v[0]); }

-----Original Message----- From: boost-users-bounces@lists.boost.org [mailto:boost-users-bounces@lists.boost.org] On Behalf Of Steven Watanabe Sent: 20 November 2008 16:12 To: boost-users@lists.boost.org Subject: Re: [Boost-users] [array] with variable size

AMDG

Hicham Mouline wrote:

...
I have a third-party library that gives me a number N of doubles, then expects from me a double* to an array where it will set N elements

This would have happen many times and N is variable, so I wish not to reallocate the array each time.

Can't you use a vector and resize it every time?

In Christ, Steven Watanabe

_______________________________________________ Boost-users mailing list Boost-users@lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users

Regards, Andy.

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Boris

5:11 p.m.

On Thu, 20 Nov 2008 17:00:51 +0100, Hicham Mouline wrote:

Hello,

I have a third-party library that gives me a number N of doubles, then expects from me a double* to an array where it will set N elements

This would have happen many times and N is variable, so I wish not to reallocate the array each time.

I know however N is maxed at some value Nmax like 50.

I thought of using a array that would be allocated once, then perhaps have a wrapper around it so that only N elements of it can be accessed.

This seems to be a usual idiom, are there ready implementations?

See boost_carray.zip from http://www.boostpro.com/vault/. Boris

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participants (5)

Andy Tompkins
Boris
Emil Dotchevski
Hicham Mouline
Steven Watanabe