array of structures initialization

[Steve]

A coworker just returned to C++ coding after a long hiatus and asked me how
to accomplish this task. What seemed liked simple issue, we have been unable
to resolve. He has declared a structure that includes an MFC class and wants
to initialize it at declaration time. Something like this:

In the h. file:

namespace SomeNamespace
{

struct SomeStruct
{
long theNumber;
CPoint thePoint;
};

SomeStruct arrssTheArray[] =
{
{
1,
CPoint(1,1)
},
{
2,
CPoint(2,2)
}
};
};

I have about 5 years experience in C\C++ but am self-taught so I can't rely
on any training background and I have been unable to find a similar example
of code. The compiler compliains that is cannot cast the long to a
"SomeStruct ".

We also tried:

In the .h file:

namespace SomeNamespace
{

struct SomeStruct
{
long theNumber;
CPoint thePoint;
};

SomeStruct arrssTheArray[];
};

In the .cpp file:

#include "SomeFile.h "

SomeNamespace:: SomeStruct SomeNamespace:: arrssTheArray[] =
{
{
1,
CPoint(1,1)
},
{
2,
CPoint(2,2)
}
};

In this case the compiler complains about a redefinition. Can this task even
be done? Where can one go for information of this sort? I have about ~4
books on C\C++ but cannot seem to find a definitive answer for issues like
this. Thanks all.

Steve

[Rob Williscroft]

Re: array of structures initialization

Steve wrote in news:I7zr9q.Inr @news.boeing.co m in comp.lang.c++:
[color=blue]
> A coworker just returned to C++ coding after a long hiatus and asked
> me how to accomplish this task. What seemed liked simple issue, we
> have been unable to resolve. He has declared a structure that includes
> an MFC class and wants to initialize it at declaration time. Something
> like this:
>[/color]

#include <iostream>
#include <utility>

/** Simple hack to post *compilable* code
*/
typedef std::pair< int, int > CPoint;

namespace SomeNamespace
{
struct SomeStruct
{
long theNumber;
CPoint thePoint;
};

SomeStruct a[] =
{
{ 1, CPoint(1,1) },
{ 2, CPoint(2,2) }
};

/** Needs to extern otherwise its a *defenition*
*/
extern SomeStruct b[];
}

/** NOT a redefenition as the above is only a declaration
*/
SomeNamespace:: SomeStruct SomeNamespace:: b[] =
{
{ 1, CPoint(1,1) },
{ 2, CPoint(2,2) }
};

int main()
{
std::cout << SomeNamespace:: a[1].thePoint.first << '\n';
std::cout << SomeNamespace:: b[1].thePoint.first << '\n';
}

The above compiles fine with every compiler I tried, including
MSVC 7.1.

HTH.

Rob.
--

http://www.victim-prime.dsl.pipex.com/

[Steve]

Re: array of structures initialization

Thank you Rob, but no dice... exact code I used:

namespace Something
{
typedef std::pair< int, int > CPoint;

struct SomeStruct
{
long theNumber;
CPoint thePoint;
};

extern SomeStruct b[];
}

Something::Some Struct Something::b[] =
{
{ 1, CPoint(1,1) },
{ 2, CPoint(2,2) }
};

Produces the following error using VC6.

error C2440: 'initializing' : cannot convert from 'const int' to 'struct
JSOWCT::SomeStr uct'
No constructor could take the source type, or constructor overload
resolution was ambiguous

????
Thanks again.
Steve


"Rob Williscroft" <rtw@freenet.co .uk> wrote in message
news:Xns95B1884 9C58E6ukcoREMOV Efreenetrtw@130 .133.1.4...[color=blue]
> Steve wrote in news:I7zr9q.Inr @news.boeing.co m in comp.lang.c++:
>[color=green]
> > A coworker just returned to C++ coding after a long hiatus and asked
> > me how to accomplish this task. What seemed liked simple issue, we
> > have been unable to resolve. He has declared a structure that includes
> > an MFC class and wants to initialize it at declaration time. Something
> > like this:
> >[/color]
>
> #include <iostream>
> #include <utility>
>
> /** Simple hack to post *compilable* code
> */
> typedef std::pair< int, int > CPoint;
>
> namespace SomeNamespace
> {
> struct SomeStruct
> {
> long theNumber;
> CPoint thePoint;
> };
>
> SomeStruct a[] =
> {
> { 1, CPoint(1,1) },
> { 2, CPoint(2,2) }
> };
>
> /** Needs to extern otherwise its a *defenition*
> */
> extern SomeStruct b[];
> }
>
> /** NOT a redefenition as the above is only a declaration
> */
> SomeNamespace:: SomeStruct SomeNamespace:: b[] =
> {
> { 1, CPoint(1,1) },
> { 2, CPoint(2,2) }
> };
>
> int main()
> {
> std::cout << SomeNamespace:: a[1].thePoint.first << '\n';
> std::cout << SomeNamespace:: b[1].thePoint.first << '\n';
> }
>
> The above compiles fine with every compiler I tried, including
> MSVC 7.1.
>
> HTH.
>
> Rob.
> --
> http://www.victim-prime.dsl.pipex.com/[/color]

[Victor Bazarov]

Re: array of structures initialization

Steve wrote:[color=blue]
> Thank you Rob, but no dice... exact code I used:
>
> namespace Something
> {
> typedef std::pair< int, int > CPoint;
>
> struct SomeStruct
> {
> long theNumber;
> CPoint thePoint;
> };
>
> extern SomeStruct b[];
> }
>
> Something::Some Struct Something::b[] =
> {
> { 1, CPoint(1,1) },[/color]

Try adding a constructor to your SomeStruct:

struct SomeStruct
{
long theNumber;
CPoint thePoint;
SomeStruct(long N, int i1, int i2)
: theNumber(N), thePoint(std::m ake_pair(i1,i2) ) {}
};

and initialising it like this:

SomeStruct(1, 1, 1)

[color=blue]
> { 2, CPoint(2,2) }
> };
>
> Produces the following error using VC6.
>
> error C2440: 'initializing' : cannot convert from 'const int' to 'struct
> JSOWCT::SomeStr uct'
> No constructor could take the source type, or constructor overload
> resolution was ambiguous
>
> ????[/color]

And upgrade your compiler to v7.1 ASAP.
[color=blue]
> Thanks again.
> Steve
> [...][/color]

And don't top-post.

V