Initialization of an array

[jamx]

How can you initialize an array, in the initialization list of a
constructor ??

SomeClass
{
public:
SomeClass() : *init here* { }
private:
int some_array[2];
};

[Victor Bazarov]

jamx wrote:

How can you initialize an array, in the initialization list of a
constructor ??

SomeClass
{
public:
SomeClass() : *init here* { }
private:
int some_array[2];
};

You cannot.

V
--
Please remove capital 'A's when replying by e-mail
I do not respond to top-posted replies, please don't ask

[=?ISO-8859-15?Q?Juli=E1n?= Albo]

jamx wrote:

How can you initialize an array, in the initialization list of a
constructor ??

SomeClass
{
public:
SomeClass() : *init here* { }
private:
int some_array[2];
};

You can't do it directly, but you can use some like this:

class Init
{
public:
Init (int (& array ) [2])
{
array [0]= 42;
array [1]= 43;
}
};

class SomeClass : private Init
{
public:
SomeClass() : Init (some_array) { }
private:
int some_array[2];
};

--
Salu2

[Alf P. Steinbach]

* Victor Bazarov:

jamx wrote:

>How can you initialize an array, in the initialization list of a
constructor ??

SomeClass
{
public:
SomeClass() : *init here* { }
private:
int some_array[2];
};

You cannot.

Well, you can zero-initialize it.

--
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[Pavel]

jamx wrote:

How can you initialize an array, in the initialization list of a
constructor ??

SomeClass
{
public:
SomeClass() : *init here* { }
private:
int some_array[2];
};

I would simply initialize it in the constructor's body (actually, member
initialization is the constructor's bread-n-butter):
SomeClass() {
// *init some_array here */
}

[Grizlyk]

Julian Albo wrote:

>

>How can you initialize an array, in the initialization list of a
constructor ??

SomeClass
{
public:
SomeClass() : *init here* { }
private:
int some_array[2];
};

You can't do it directly, but you can use some like this:

class Init
{
public:
Init (int (& array ) [2])
{
array [0]= 42;
array [1]= 43;

Note: it is assignment rather than initialization: "default ctor +
operator=".

--
Maksim A. Polyanin
http://grizlyk1.narod.ru/cpp_new

"In thi world of fairy tales rolls are liked olso"
/Gnume/

[jamx]

On 25 feb, 22:29, "Alf P. Steinbach" <[e-mail] rote:

* Victor Bazarov:

jamx wrote:

How can you initialize an array, in the initialization list of a
constructor ??

SomeClass
{
public:
SomeClass() : *init here* { }
private:
int some_array[2];
};

You cannot.

Well, you can zero-initialize it.

--
A: Because it messes up the order in which people normally read text.
Q: Why is it such a bad thing?
A: Top-posting.
Q: What is the most annoying thing on usenet and in e-mail?

Thats what i want, to initialize them with zero ;-)

[Alf P. Steinbach]

* jamx:

On 25 feb, 22:29, "Alf P. Steinbach" <[e-mail] rote:

>* Victor Bazarov:

>>jamx wrote:
How can you initialize an array, in the initialization list of a
constructo r ??
SomeClass
{
public:
SomeClass() : *init here* { }
private:
int some_array[2];
};
You cannot.

Well, you can zero-initialize it.

Thats what i want, to initialize them with zero ;-)

Please don't quote signatures -- corrected.

In standard C++ you just write

struct SomeClass
{
SomeClass(): some_array() {}
int some_array[2];
};

Some compilers (notably old Visual C++, IIRC) don't support that, i.e.
they're not standard-conforming, but for such compilers you can employ
the artificial base class trick:

struct SomeClassMember s
{
int some_array[2];
};

struct SomeClass: SomeClassMember s
{
SomeClass(): SomeClassMember s() {}
};

However, no matter whether your compiler is standard-conforming in this
respect or not, you're probably much better off using a std::vector than
a raw array, i.e.

struct SomeClass
{
SomeClass(): some_array(2) {}
std::vector<int some_array;
};

--
A: Because it messes up the order in which people normally read text.
Q: Why is it such a bad thing?
A: Top-posting.
Q: What is the most annoying thing on usenet and in e-mail?

[jamx]

On 26 feb, 09:41, "Alf P. Steinbach" <[e-mail] rote:

* jamx:

On 25 feb, 22:29, "Alf P. Steinbach" <[e-mail] rote:

* Victor Bazarov:

>jamx wrote:
How can you initialize an array, in the initialization list of a
constructor ??
SomeClass
{
public:
SomeClass() : *init here* { }
private:
int some_array[2];
};
You cannot.
Well, you can zero-initialize it.

Thats what i want, to initialize them with zero ;-)

Please don't quote signatures -- corrected.

In standard C++ you just write

struct SomeClass
{
SomeClass(): some_array() {}
int some_array[2];
};

Some compilers (notably old Visual C++, IIRC) don't support that, i.e.
they're not standard-conforming, but for such compilers you can employ
the artificial base class trick:

struct SomeClassMember s
{
int some_array[2];
};

struct SomeClass: SomeClassMember s
{
SomeClass(): SomeClassMember s() {}
};

However, no matter whether your compiler is standard-conforming in this
respect or not, you're probably much better off using a std::vector than
a raw array, i.e.

struct SomeClass
{
SomeClass(): some_array(2) {}
std::vector<int some_array;
};

--
A: Because it messes up the order in which people normally read text.
Q: Why is it such a bad thing?
A: Top-posting.
Q: What is the most annoying thing on usenet and in e-mail?

It's for BSD/UNIX, so i'm using gcc. I will try out this Someclass() :
some_arra() {} construction, thanks.

I agree, that most of the time a vector is the better choise. But
since pipe() requires an "int fildes[2]", i will use an array.

[Gavin Deane]

On 26 Feb, 12:31, "jamx" <debraban...@gm ail.comwrote:

I agree, that most of the time a vector is the better choise. But
since pipe() requires an "int fildes[2]", i will use an array.

As it happens, none of that prevents you using a vector if you want
to.

pipe might say it takes an int fildes[2] but C and C++ don't let you
be that precise in function declarations. In fact, pipe takes just an
int* and it is entirely your responsibility to make sure that that
pointer points to the first element of an array with (at least) 2
elements. You can equally well do

vector<intv(2);
pipe(&v[0]);

which allows you to continue to use containers in your own code. Raw
arrays and pointers don't need to propogate outside the API you are
using.

Gavin Deane