C / C++ / MFC

Re: accessing the elements of a struct from another class

10-Jul-03 10:04

Saying "struct container" is redundant as a struct is a container of (different) data types.

That aside, I'm not sure what you are asking. Your RFMAccess class has a TSimHeader structure in it with 10 instances defined. In order to access any one instance, you'll need to use square brackets like you've shown. It makes no difference whether you use TSimHeader_arr[i], or s[i].

Here's a kludgy example:

class MyOtherClass
{
    // a pointer to a single instance
    struct RFMAccess::TSimHeader *ts;

    void foo( int x )
    {
        // point to the instance
        ts = &(RFMAccess::TSimHeader_arr[x]);
    }
};

You could also add the following function to your RFMAccess class:

static struct TSimHeader *GetSingleInstance( int x )
{
    return (&TSimHeader_arr[x]);
}

And use it in another class like:

void foo2( void )
{
    struct RFMAccess::TSimHeader *ts;
    ts = RFMAccess::GetSingleInstance(0);
}

Notice that qualification is still necessary for both usages.

johnstonsk10-Jul-03 10:20

johnstonsk

10-Jul-03 10:20

OK I see what you are saying,

Thanks,
steven

(cin>>x).get( );

DaveE9th10-Jul-03 7:44

10-Jul-03 7:44

I was reading that a function always requires a return, but I don't see one for the statement below. I've posted the entire program below also. Thanks. OMG | :OMG:

(cin>>x).get();

----------------------------------------------------------
#include "iostream.h"
#include "string.h"

int main()
{
int x;
int i;
char str[80];
bool isfinished=false;
char Info [] [300] =
{
"3030-02-000-5287" , "Here is the information for this number." ,
"3030-03-000-0029" , "Here is the information for this number." ,
};
while(isfinished==false)
{
cout<<"\nPlease enter a number:\n";
cin>>str;
for(i=0; i < 4; i += 2)
if(!strcmp(str, Info[i]))
{
cout<<"\nInformation:"<<info[i+1]<<"\n";
break;
="" }
="" if(i="=" 4)
="" {
="" cout<<"number="" not="" found.\n";
=""
="" cout<<"\nwould="" you="" like="" to="" check="" another?\n";
="" cout<<"enter="" 1="" for="" yes,="" 0="" no.\n";
="" (cin="">>x).get();//no return?

}
if (x==0) isfinished=true;
}
return 0;
}

Nick Parker10-Jul-03 8:25

Nick Parker

10-Jul-03 8:25

DaveE9th wrote:
(cin>>x).get();//no return?

It appears to be a typo (or I am wrong). It should either be:

cin >> x;

int x = cin.get();

-Nick Parker

John M. Drescher10-Jul-03 10:38

John M. Drescher

10-Jul-03 10:38

DaveE9th wrote:
if (x==0) isfinished=true;

This is incorrect. It should be

if (x == '0') isfinished=true;

John

Michael Dunn10-Jul-03 13:30

Michael Dunn

10-Jul-03 13:30

(cin>>x).get() is a confusing way of writing:

cin >> x;<br />
cin.get();

The >> opertor returns a reference to the stream, so you can call the get() method on the return value.

--Mike--
"I'm working really, really fast at the moment, so a 3 minute outage becomes, due to time dilation, a 5 minute outage."
-- Chris Maunder, relativistic system administrator
Ericahist | Homepage | RightClick-Encrypt | 1ClickPicGrabber

Nick Parker10-Jul-03 18:10

Nick Parker

10-Jul-03 18:10

Interesting, I thought it looked like a typo.

Learn something new every day. Big Grin | :-D

-Nick Parker

DaveE9th10-Jul-03 21:57

10-Jul-03 21:57

I still don't quite understand why function "get();" doesn't need a return. Why is this?

Thanks, Dave
Hmmm | :|

Ryan Binns10-Jul-03 22:46

Ryan Binns

10-Jul-03 22:46

The get() function with no parameters reads and returns the next character from the stream. If this character is not required (eg. you simply need to skip to the next character) then there is no use for the return value.

Ryan

"Punctuality is only a virtue for those who aren't smart enough to think of good excuses for being late" John Nichol "Point Of Impact"

DaveE9th11-Jul-03 7:27

11-Jul-03 7:27

I read that if a function did not return a value that (at a minimum) you had to use the "void" prototype...such as below:

void main( )

no?

hmmmmm

Dave

OMG | :OMG:

Ryan Binns11-Jul-03 15:59

Ryan Binns

11-Jul-03 15:59

The get() function returns a value - the value of the next character read. This program simply doesn't use the returned value.

Ryan

"Punctuality is only a virtue for those who aren't smart enough to think of good excuses for being late" John Nichol "Point Of Impact"

DaveE9th12-Jul-03 2:29

12-Jul-03 2:29

Thanks Ryan

"The man who reads nothing is better educated than the man who reads nothing but
newspapers."- Thomas Jefferson

btrees in STL

Anonymous10-Jul-03 7:43

Anonymous

10-Jul-03 7:43

is there an implementation of btrees in STL?

valikac10-Jul-03 7:48

valikac

10-Jul-03 7:48

Are you referring to a binary tree structure? If yes, STL containers including set and map are designed using binary stree structure.

Kuphryn

David Crow10-Jul-03 8:58

10-Jul-03 8:58

By btree, do you mean a binary tree, which can be lopsided, or a B-tree, which is always balanced?

Anonymous10-Jul-03 12:24

Anonymous

10-Jul-03 12:24

a balanced tree that is.

however, any kind of a tree I guess wouldn't be bad. Anything like CTreeCtrl in MFC even?

David Crow11-Jul-03 3:08

11-Jul-03 3:08

B-tree, red/black tree, splay tree, and AVL tree are all examples of balanced trees, each with their own set of nuances.

The CTreeCtrl class is for displaying a hierarchical list of items, much like Windows Explorer.

input/change/delete array elements

Nemanja Trifunovic10-Jul-03 9:09

Nemanja Trifunovic

10-Jul-03 9:09

B-Tree?[^]

Not that I know of, and I've been searching for it for quite a bit.

DaveE9th10-Jul-03 7:37

Re: input/change/delete array elements

10-Jul-03 7:37

I want to be able to allow the user to modify the numbers in the array of the working program below. I want to enable the user to have the ability to delete, change or add a new number into the array. What would be my best approach to do this? Thanks much, Dave

-------------------------------------------------------------------
#include "iostream.h"
#include "string.h"

int main()
{
int x;
int i;
char str[80];
bool isfinished=false;
char Info [] [300] =
{
"6787-02-000-5287" , "Here is the information for this number." ,
"5978-03-000-0029" , "Here is the information for this number." ,
};
while(isfinished==false)
{
cout<<"\nPlease enter a number:\n";
cin>>str;
for(i=0; i < 4; i += 2)
if(!strcmp(str, Info[i]))
{
cout<<"\nInformation:"<<info[i+1]<<"\n";
break;=""
}=""
if(i="=" 4)=""
{=""
cout<<"number="" not="" found.\n";=""

cout<<"\nwould="" you="" like="" to="" check="" another?\n";=""

{=""
cout<<"enter="" 1="" for="" yes,="" 0="" no.\n";=""
(cin="">>x).get();

}
if (x==0) isfinished=true;
}
return 0;
}

valikac10-Jul-03 7:49

valikac

10-Jul-03 7:49

One solution is and STL list container.

Kuphryn

Re: input/change/delete array elements

David Crow10-Jul-03 9:06

Re: input/change/delete array elements

10-Jul-03 9:06

It depends on what you are after. As I understand it, you'd want a simply menu like:

 CHOICES
----------
1. Display
2. Delete
3. Change
4. Add

If the user chose #1, you'd print the current contents of the array using code similar to what you've shown.

If the user chose #2, you'd prompt for the array index to delete. All items in the array after that index would probably need to be moved "up" in the order to fill in the hole.

If the user chose #3, you'd again prompt for: 1) the array index, 2) the part number, and 3) the part number description. The array item at the specified index would then be updated with these new values.

If the user chose #4, you'd prompt for the part number and the part number description. These values would then be assigned to the next available index.

DaveE9th10-Jul-03 22:05