new/ resize

[machine99]

how do you resize an array allocated with new?

[Rolf Magnus]

machine99 wrote:

how do you resize an array allocated with new?

You don't. Yo have to allocate a new block of memory of the target size
and then move the data there and deallocate the original array.
Any reason why you don't use std::vector, which handles resizing for
you?

[machine99]

> > how do you resize an array allocated with new?

You don't. Yo have to allocate a new block of memory of the target size
and then move the data there and deallocate the original array.
Any reason why you don't use std::vector, which handles resizing for
you?

I do use std::vector quite extensively but there will always be special
cases :)

[Thomas Matthews]

machine99 wrote:

how do you resize an array allocated with new?

You don't. Yo have to allocate a new block of memory of the target size
and then move the data there and deallocate the original array.
Any reason why you don't use std::vector, which handles resizing for
you?

I do use std::vector quite extensively but there will always be special
cases :)

Actually, the situations where an array is preferred or required
over a std::vector are few and don't require resizing.

Some of these situations are code / memory space and execution time.
However, time spent developing (and development cost) usually
outweighs any premature optimization issues and all problems
involved with an array when a std::vector should have been used.

The programming priorities (listed with highest priority first):
1. Quality & robustness
2. Development time (also related to cost).
3. User interaction or interaction with the environment.
4. Code space and execution time (i.e. optimization).
If a program can't correctly turn a motor, turning it faster
or using less code to turn it is a mute point.

--
Thomas Matthews

C++ newsgroup welcome message:
http://www.slack.net/~shiva/welcome.txt
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Other sites:
http://www.josuttis.com -- C++ STL Library book
http://www.sgi.com/tech/stl -- Standard Template Library

[Thomas Matthews]

Thomas Matthews wrote:

machine99 wrote:

how do you resize an array allocated with new?
You don't. Yo have to allocate a new block of memory of the target size
and then move the data there and deallocate the original array.
Any reason why you don't use std::vector, which handles resizing for
you?

I do use std::vector quite extensively but there will always be special
cases :)

Actually, the situations where an array is preferred or required
over a std::vector are few and don't require resizing.

Some of these situations are code / memory space and execution time.
However, time spent developing (and development cost) usually
outweighs any premature optimization issues and all problems
involved with an array when a std::vector should have been used.

The programming priorities (listed with highest priority first):
1. Quality & robustness
2. Development time (also related to cost).
3. User interaction or interaction with the environment.
4. Code space and execution time (i.e. optimization).
If a program can't correctly turn a motor, turning it faster
or using less code to turn it is a mute point.

Oops, that should be "moot point".

--
Thomas Matthews

C++ newsgroup welcome message:
http://www.slack.net/~shiva/welcome.txt
C++ Faq: http://www.parashift.com/c++-faq-lite
C Faq: http://www.eskimo.com/~scs/c-faq/top.html
alt.comp.lang.l earn.c-c++ faq:
http://www.raos.demon.uk/acllc-c++/faq.html
Other sites:
http://www.josuttis.com -- C++ STL Library book
http://www.sgi.com/tech/stl -- Standard Template Library

[Howard]

"Thomas Matthews" <Th************ *************** *@sbcglobal.net > wrote in
message news:3F******** **@sbcglobal.ne t...

machine99 wrote:

how do you resize an array allocated with new?

You don't. Yo have to allocate a new block of memory of the target size
and then move the data there and deallocate the original array.
Any reason why you don't use std::vector, which handles resizing for
you?

I do use std::vector quite extensively but there will always be special
cases :)

Actually, the situations where an array is preferred or required
over a std::vector are few and don't require resizing.

Why does the need to resize an array mean that it is no longer neccessary to
use an array instead of a vector?
Some of these situations are code / memory space and execution time.
However, time spent developing (and development cost) usually
outweighs any premature optimization issues and all problems
involved with an array when a std::vector should have been used.

The programming priorities (listed with highest priority first):
1. Quality & robustness
2. Development time (also related to cost).
3. User interaction or interaction with the environment.
4. Code space and execution time (i.e. optimization).
If a program can't correctly turn a motor, turning it faster
or using less code to turn it is a mute point.

--

You're missing one of the most important priorities for many of us:
compatibility with existing code. We don't all get to choose how we would
write code. Much of it is forced upon us by what was written before, (or by
what our operating system or third-party API's require).

-Howard

[Andreas Müller]

"Howard" wrote:

"Thomas Matthews" <Th************ *************** *@sbcglobal.net >
wrote in message news:3F******** **@sbcglobal.ne t...

machine99 wrote:

[snip] You're missing one of the most important priorities for many of us:
compatibility with existing code. We don't all get to choose how we
would write code. Much of it is forced upon us by what was written
before, (or by what our operating system or third-party API's
require).

-Howard

When it comes to a point where compatibility to arrays comes into the
game, I usually stick with std::vector, as I can easily pass the content
of a vector into a legacy function (&vector[0]) and converting a
returned array into a vector normally doesn't affect performance in the
stuff that I do. (If it does and it was proven by a profiler, then that
is another story!)
--
To mail me directly, remove the NO*SPAM parts in
NO***********@g mx.netNO*SPAM

[Thomas Matthews]

Howard wrote:

"Thomas Matthews" <Th************ *************** *@sbcglobal.net > wrote in
message news:3F******** **@sbcglobal.ne t...

Why does the need to resize an array mean that it is no longer neccessary to
use an array instead of a vector?
IMHO, the primary difference between a vector and an array is the
resizing issue. By the C++ definition, an array is a static structure
in that its size doesn't change. If the array size changes, then a
vector is a better choice (since the code already exists for
resizing and has been tested). There are other qualities of a
vector, such as bounds checking, that are useful during the
development stage.

Some of these situations are code / memory space and execution time.
However, time spent developing (and development cost) usually
outweighs any premature optimization issues and all problems
involved with an array when a std::vector should have been used.

The programming priorities (listed with highest priority first):
1. Quality & robustness
2. Development time (also related to cost).
3. User interaction or interaction with the environment.
4. Code space and execution time (i.e. optimization).
If a program can't correctly turn a motor, turning it faster
or using less code to turn it is a mute point.

--

You're missing one of the most important priorities for many of us:
compatibility with existing code. We don't all get to choose how we would
write code. Much of it is forced upon us by what was written before, (or by
what our operating system or third-party API's require).

-Howard

I still believe that quality and robustness is top priority especially
when maintaining legacy systems. I know from personal experience that
small changes can cause an existing system to blow up (primarily due
to undocumented dependencies).

Don't get me wrong, compatibility is an issue. A correct modification
that takes more time to develop is better than a quick and dirty fix
that isn't 100% correct. Also, if the new code is not compatible
with the existing code, it is worthless. I would place compatibility
under quality and robustness.

--
Thomas Matthews

C++ newsgroup welcome message:
http://www.slack.net/~shiva/welcome.txt
C++ Faq: http://www.parashift.com/c++-faq-lite
C Faq: http://www.eskimo.com/~scs/c-faq/top.html
alt.comp.lang.l earn.c-c++ faq:
http://www.raos.demon.uk/acllc-c++/faq.html
Other sites:
http://www.josuttis.com -- C++ STL Library book

[machine99]

How does std::vector resize then?

Perhaps I could access its memory functions/classes/whatever and use them
for my own purpose?

[Christopher Benson-Manica]

Rolf Magnus <ra******@t-online.de> spoke thus:

You don't. Yo have to allocate a new block of memory of the target size
and then move the data there and deallocate the original array.
Any reason why you don't use std::vector, which handles resizing for
you?

Just for curiosity's sake, why isn't there something like realloc() for new?
Wouldn't that make situations like this one easier to manage?

--
Christopher Benson-Manica | I *should* know what I'm talking about - if I
ataru(at)cybers pace.org | don't, I need to know. Flames welcome.