Help with vectors

[SVincent240]

I am having a problem creating a vector of type struct. this is my code that will not work:
[code=cpp]
//Initialization steps prior to code.
#include <iostream>
#include <vector>
#include <iomanip>
#include <fstream>
#include <string>
using namespace std;

int main ()
{

char letter;
int numb = 0;

struct acct
{
char first [15];
char last [15];
char ssn [9];
char logon [8];
};

vector <acct> accounts;

ifstream roster; //These lines initialize the text file containing the account data.
roster.open("/roster.txt");
if (roster.fail()) return 1;
[/code]

the error msg is:

error: 'main()::acct' uses local type 'main()::acct'
error: trying to instantiate 'template<class _Alloc> class std::allocator'
error: template argument 2 is invalid
error: invalid type in declaration before ';' token

[Ganon11]

Try moving your struct definition outside of main().

[weaknessforcats]

What compiler are youusing?

Your code example compiles and links using Visual Studio.NET 2008.

[vmpstr]

It doesn't compile on g++ 4.2.4
Making the struct definition global produces a different kind of error. But, if the struct is made global and the line
vector <acct> accounts;
is replaced with
vector <struct acct> accounts;
it compiles and links

[weaknessforcats]

Making the struct definition global produces a different kind of error. But, if the struct is made global and the line
vector <acct> accounts;
is replaced with
vector <struct acct> accounts;
it compiles and links

I don't understand your reply: a) when you say struct definition, do you mean declaration? b) what is the difference between (a) and struct is made global ? and c) C++ does not require the use of struct when referring to a user defined type.

[vmpstr]

I don't understand your reply: a) when you say struct definition, do you mean declaration? b) what is the difference between (a) and struct is made global ? and c) C++ does not require the use of struct when referring to a user defined type.

I've always been very week in my terminology. I apologize for that. I believe it's called "type definition". I'm referring to the chunk of code that is something along the lines of the following:

struct a
{
    int i;
};

By "struct made global", I'm referring to the previous reply (by Ganon11) which suggested that the struct definition should be moved outside of the function.

Lastly, I agree that C++ does not require struct keyword. This has been my experience as well, although I tend to put it there anyway. However, without the struct keyword in the parameter to the template, I get the following messages on g++ (when compiling the code posted above)

~/test$ g++ compileme.cpp
compileme.cpp: In function ‘int main()’:
compileme.cpp:23: error: type/value mismatch at argument 1 in template parameter list for ‘template<class _Tp, class _Alloc> class std::vector’
compileme.cpp:23: error:   expected a type, got ‘acct’
compileme.cpp:23: error: template argument 2 is invalid
compileme.cpp:23: error: invalid type in declaration before ‘;’ token

I don't claim that putting struct keyword there is good style or bad style. I simply say that it seems to be the only way to compile that code. This might be simply a g++ problem...

I hope this clears it up a little bit.

[weaknessforcats]

This looks like a g++ problem.

As I say, your original code is OK and does compile and link with Visual Studio.NET 2008.

The g++ complaint about expecting a type and got acct is odd since acct is a type. Worse, when vector<struct acct> works and vector<acct doesn't leads one to think that g++ thinks it's compiling C.

As to definition vs declaration, the difference is that a definition occupies memory while a declaration does not.

These are declarations:

struct X   //or class X
{
    int a;
};

extern int data;

enum Colors {RED, BLUE, GREEN};

void A Function(int, int);

Whereas these are definitions:

X    Avariable:

int data;

Colors MyColor = RED;

void A Function(int, int)
{
   //do something
}

[vmpstr]

Hmm... Thanks for explaining that, it makes a bit easier to think about definitions and declarations.

:D