vector<bool>

[Piotr]

In effective STL, it said one should not use vector<bool> but use
dequeue<bool> instead.

But can dequeue<bool> has random access iterator? and I do this?
dequeue<bool> myboolarray;
if (myboolarray[3]) {
// do this...
}

if not, is there another solution?

Thank you.

[Luke Meyers]

Piotr wrote:

In effective STL, it said one should not use vector<bool> but use
dequeue<bool> instead.

But can dequeue<bool> has random access iterator? and I do this?
dequeue<bool> myboolarray;
if (myboolarray[3]) {
// do this...
}

Teach a man to fish...

http://www.sgi.com/tech/stl/Deque.html

(Which Effective C++ Item# is RTFM?)

Luke

P.S. Yes.

[Thomas Tutone]

Piotr wrote:

In effective STL, it said one should not use vector<bool> but use
dequeue<bool> instead.
The container is called a "deque", not a "dequeue." Leaving aside the
spelling error, that's often good advice, unless you can live with
vector<bool>'s limitations.
But can dequeue<bool> has random access iterator?
Yes, but again, it's a deque<bool>, not dequeue<bool>.
and I do this?
dequeue<bool> myboolarray;
if (myboolarray[3]) {
// do this...
}

Yes, if you fix the spelling error.

Best regards,

Tom

[samuel.y.l.cheung]

Thanks. I tried this, but it fails with this compiler error:

Matcher.h:11: error: ISO C++ forbids declaration of 'deque' with no
type
Matcher.h:11: error: expected ';' before '<' token

Can you please tell me why?
#include <deque>
#include <algorithm>

class Matcher {

protected:
deque<bool> content;
};

[m_schellens]

try

std::deque<bool > content;

instead.
Cheers,
Marc

[Alan Johnson]

sa************* **@gmail.com wrote:

Thanks. I tried this, but it fails with this compiler error:

Matcher.h:11: error: ISO C++ forbids declaration of 'deque' with no
type
Matcher.h:11: error: expected ';' before '<' token

Can you please tell me why?
#include <deque>
#include <algorithm>

class Matcher {

protected:
deque<bool> content;
};

Try std::deque<bool > content;

Alan

[Ian Collins]

sa************* **@gmail.com wrote:

Thanks. I tried this, but it fails with this compiler error:
Thanks for what? Please quote!
Matcher.h:11: error: ISO C++ forbids declaration of 'deque' with no
type
Matcher.h:11: error: expected ';' before '<' token

Can you please tell me why?
#include <deque>
#include <algorithm>

class Matcher {

protected:
deque<bool> content;

std::deque<bool > content;

--
Ian Collins.

[Ivan Vecerina]

"Piotr" <ra************ @gmail.com> wrote in message
news:11******** **************@ f14g2000cwb.goo glegroups.com.. .
: In effective STL, it said one should not use vector<bool> but use
: dequeue<bool> instead.
:
: But can dequeue<bool> has random access iterator? and I do this?
: dequeue<bool> myboolarray;
: if (myboolarray[3]) {
: // do this...
: }
:
: if not, is there another solution?

Yet another alternative might be to store bools into a:
std::vector<uns igned char>
This of course has caveats if you rely on implicit
conversions when storing new elements.

You may also want to consider std::bitset, and maybe you don't
need to care about the flaws of std::vector<boo l>.
hth,
Ivan
--
http://ivan.vecerina.com/contact/?subject=NG_POST <- email contact form
Brainbench MVP for C++ <> http://www.brainbench.com

[Michiel.Salters]

Ivan Vecerina wrote:

"Piotr" <ra************ @gmail.com> wrote in message
news:11******** **************@ f14g2000cwb.goo glegroups.com.. .
: In effective STL, it said one should not use vector<bool> but use
: dequeue<bool> instead....
is there another solution?

Yet another alternative might be to store bools into a:
std::vector<uns igned char>

The reason to avoid std::vector<boo l> is because it doesn't contain
genuine bools. If you can live with std::vector<uns igned char>, you
definitely
don't need genuine bools. So your replacement works only if it is not
needed, sorry.

Michiel Salters

[Ivan Vecerina]

<Mi************ *@tomtom.com> wrote in message
news:11******** **************@ g47g2000cwa.goo glegroups.com.. .
: Ivan Vecerina wrote:
: > "Piotr" <ra************ @gmail.com> wrote in message
: > news:11******** **************@ f14g2000cwb.goo glegroups.com.. .
: > : In effective STL, it said one should not use vector<bool> but use
: > : dequeue<bool> instead....
: > is there another solution?
: >
: > Yet another alternative might be to store bools into a:
: > std::vector<uns igned char>
:
: The reason to avoid std::vector<boo l> is because it doesn't contain
: genuine bools. If you can live with std::vector<uns igned char>, you
: definitely don't need genuine bools. So your replacement works only
: if it is not needed, sorry.

This seems like a very decisive all-encompassing statement.
I do not agree that 'needing references to bool elements'
is the only reason to avoid vector<bool>.
The requirement could be to 'store true/false values in a contiguous
array', and then deque<bool> won't do, but vector<uchar> might.
A trade-off does exist.

For example, I happen to use 'unsigned char' buffers to store
B/W 'binary' images - even when only a bool really is needed.
A contiguous buffer addressable with plain pointers facilitates
the implementation of image processing algorithms.

Peace,
Ivan

--
http://ivan.vecerina.com/contact/?subject=NG_POST <- email contact form
Brainbench MVP for C++ <> http://www.brainbench.com