[quote name='Misery' timestamp='1309620650' post='4830366']
Does something like vector<bool> tell You guys something?

I'm not following. You can have containers of objects, no problem.
[/quote]


Blind guess: He's probably referring to the overhead. Well, you also have the same with an array of bools. If you want to use only a single bit for each bool you need to use bitmasks on top of that. Still until now, there wasn't a single reason not to consider STL containers.

[quote name='King Joffrey' timestamp='1309621370' post='4830369']
[quote name='Misery' timestamp='1309620650' post='4830366']
Does something like vector<bool> tell You guys something?

I'm not following. You can have containers of objects, no problem.
[/quote]


Blind guess: He's probably referring to the overhead. Well, you also have the same with an array of bools. If you want to use only a single bit for each bool you need to use bitmasks on top of that. Still until now, there wasn't a single reason not to consider STL containers.
[/quote]
std::vector<bool> is a specialization that stores bools tightly packed. This is mandated by the specification.

I need resizable bool array with tightly packed data. i mean one bit = one bool value.
Second thing is that I will use millions of instances of this class. And vector<bool>
requires (with zero entries) 20 bytes of memory. At start. Thats too much.
Therefore I have decided to create a class that has ability to resize, contains chars, and has ability to access every bit in char.
The only last problem is how to resize this fast.

Why did You guys vote down?

I need resizable bool array with tightly packed data. i mean one bit = one bool value.

std::vector<bool> is, as I've already said, tightly packed.

Second thing is that I will use millions of instances of this class. And vector<bool>
requires (with zero entries) 20 bytes of memory. At start. Thats too much.
Therefore I have decided to create a class that has ability to resize, contains chars, and has ability to access every bit in char.
The only last problem is how to resize this fast.

You need a minimum of three pointers or integers; one to hold your buffer; one to hold the allocated buffer size, or the end of the buffer, so you know when to resize; and one to hold the current size, or the current write location. Assuming two pointers and an integer, that adds up to 20 bytes (assuming a 64 bit system with 64 bit pointers and 32 bit integers). At most you can reduce two of those pointers to another integer, and perhaps the integers to smaller integer types if you want to limit the bit size, but you're still aiming at at least 10 bytes per vector.

Not to mention that there are already plenty of already implemented dynamic bit field classes.

Why did You guys vote down?

Perhaps because you came out as arrogant with your uninformed comment? You argued, for example, that you couldn't use the vector because you had to store your bools tightly packed, but an std::vector<bool> is already tightly packed. You also came out as it was something very obvious, which it apparently wasn't.

You could very easily just have stated your reasons without making such a statement.

Assuming two pointers and an integer, that adds up to 20 bytes (assuming a 64 bit system with 64 bit pointers and 32 bit integers).

To be fair, MSVC 2010 has a 20 byte std::vector<bool> even in 32 bit release builds. Its std::vector<bool> is implement in terms of std::vector<unsigned int>; it's the size of std::vector<unsigned int> plus its own data.

I have used realloc extensively in both C and C++ programs and have not had any problems. Right tool for the right job

How to do it properly? I will use memory pools anyway, but I need to finish that class I have begun.

And I'm not really a beginner, however I am not educated programmer, but fluid mechanics engineer, so many things for me are unclear.
I'm just an user of programming.

Thanks for any help.

You're posting about problems stemming from errors caused by non-constructed non-pod types (a very dangerous thing to do), but are going to criticize the standard library for having strange resizable-bool-array iterator semantics?

Are you making a resizable array of bools or a resizable array of non-pod types?

vector <bool> has not only strange non-stl semantics. It also forces compiler to optimise code inproperly. If many clever ppl say: never use vector<bool> i do not use it.
And the other thing is that vectors are quite big 20 bytes for an empty vector. One more thing is that vectors reserve much more memory than needed. I know that one can use v.reserve()
but after I exceed reserved memory it will reserve again twice more than needed and so on.
In fact I need a bit array. My basic class is byte that allows me to access every bit.