char** question...

[RAB]

I am programming in the palm environment using C++ and am stuck. I
have created an char array:

const char MyArray [300][50] =
{
{"string1"},
{"string2"},
....
{"string50"}
}

I need to build a function that will return MyArray in the form of a
char**

I need to do it this way because of memory issues.

If any looping needs to be done I would need it done with the code that
is calling the function.

Any help would be appreciated.

Thanks,
RABMissouri

[Alf P. Steinbach]

* RAB:

I am programming in the palm environment using C++ and am stuck. I
have created an char array:

const char MyArray [300][50] =
{
{"string1"},
{"string2"},
....
{"string50"}
}

Missing semicolon. Also, what you have here is three hundred strings of
max length 49, not fifty strings of max length 299. I never recall the
order because it's not something one would ordinarily use, but given a
piece of code with 2D array it's easy to check using a compiler.

I need to build a function that will return MyArray in the form of a
char**

You have a two-dimensional array, that's not the same as an array of
pointers.

One of the three requirements has to yield:

* Change the declaration of MyArray to an array of pointers.

* Change the declaration of the function to return a 'char const
(*)[300]' (or fifty, whatever was the intention).

* Discard the requirement that the function result should be MyArray
directly.

Assuming that you don't have an awful lot of memory to play around with
it seems the first point above is the best course of action, i.e.

static char const* const myArray[] =
{
"string1",
...
};
static size_t const myArray_length = sizeof(myArray)/sizeof(*myArray );

I need to do it this way because of memory issues.

Oh, yes. :-)

If any looping needs to be done I would need it done with the code that
is calling the function.

--
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?

[RAB]

Alf,

Sorry if I offended you. It was not my intention. I am just looking
for a solution.

Have you ever programmed in the palm environment? If you havent one
has 64k of ram and that is it. If one wants to store strings of data
beyond 64k one has to store exactly in the form I previously indicated.
const char MyArray [300][50] =
{
{"string1"},
{"string2"},
....
{"string300" }
};

The tricky part is I need to convert MyArray to a char** so I can put
it in a listbox.

So the question still remains, how do I convert MyArray to a char**?

Thanks,
RABMissouri

[Alf P. Steinbach]

* RAB:

Alf,

Sorry if I offended you. It was not my intention. I am just looking
for a solution.

Huh?

Have you ever programmed in the palm environment?

Nope.

If you havent one
has 64k of ram and that is it. If one wants to store strings of data
beyond 64k one has to store exactly in the form I previously indicated.

I find neither statement easy to believe... OK, 64k might be
believable, on some old late 80's early 90's palmtop. But the second
statement contradicts that, and no computer or OS I have ever heard of
places requirements on the C or C++ data layout in order to be able to
use memory -- I am quite sure you have misunderstood something.

const char MyArray [300][50] =
{
{"string1"},
{"string2"},
....
{"string300" }
};

The tricky part is I need to convert MyArray to a char** so I can put
it in a listbox.

So the question still remains, how do I convert MyArray to a char**?

Allocate an array A of 300 pointers. Initialize the pointers to point
to the strings. The address of the first element of A is your char**.

--
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?

[sun1991]

RAB wrote:

Alf,

Sorry if I offended you. It was not my intention. I am just looking
for a solution.

Have you ever programmed in the palm environment? If you havent one
has 64k of ram and that is it. If one wants to store strings of data
beyond 64k one has to store exactly in the form I previously indicated.
const char MyArray [300][50] =
{
{"string1"},
{"string2"},
....
{"string300" }
};

The tricky part is I need to convert MyArray to a char** so I can put
it in a listbox.

So the question still remains, how do I convert MyArray to a char**?

I think this maybe what you want:

char (*ptr)[50] = MyArray;

[Frederick Gotham]

RAB posted:

I need to build a function that will return MyArray in the form of a
char**

Here's a little sample code I cooked up with might be of help:

#include <iostream>
using std::cout;

unsigned const quantity_names = 50;

char const *const *GetNames()
{
/* Returns a null-terminated
array of pointers to strings. */

char const static *const arr[quantity_names] = {
"Adam", "Paul", "Philip", "James", "Matthew",
"Brian", "Thomas", "Mary", "Sandra", "Kelly",
"Lisa", "Heather" };

return arr;
}

int main()
{
for(char const *const *p = GetNames(); *p; ++p)
{
cout << *p << '\n';
}
}

--

Frederick Gotham

[RAB]

I find neither statement easy to believe... OK, 64k might be
believable, on some old late 80's early 90's palmtop. But the second
statement contradicts that, and no computer or OS I have ever heard of
places requirements on the C or C++ data layout in order to be able to
use memory -- I am quite sure you have misunderstood something.

Belive it or not, the Palm OS uses 16 bit addresses, it is quite
archaic. It makes programming a challenge. It makes one appreciate
CStrings in the Microsoft architecture.

Allocate an array A of 300 pointers.

Could you share some code please?

>Initialize the pointers to point to the strings.

Could you share some code please?

I am a hobbiest programmer and char arrays have always been a challenge
for me.

Thanks,
RABMissouri

[RAB]

Hello Sun,

char (*ptr)[50];
compiles ok
char (*ptr)[50]=MyArray;
compiler error "illegal implicit conversion from 'const
char[300][50]' to 'char (*)[50]'

Also, inorder to copy char* one must use
StrCopy(Char *dst, const Char * src); //function definition

Thanks,
RABMissouri

[RAB]

Hi Frederick,

Thanks for you help! Your code looks great.

MyArray has already been created. So I need to create a char** from
MyArray.

Another thing I should have told you, is inorder to copy arrays I need
to use the function
StrCopy( Char *dst, const Char *src);

Thanks,
RABMissouri

[Alf P. Steinbach]

* RAB:

>

>I find neither statement easy to believe... OK, 64k might be
believable, on some old late 80's early 90's palmtop. But the second
statement contradicts that, and no computer or OS I have ever heard of
places requirements on the C or C++ data layout in order to be able to
use memory -- I am quite sure you have misunderstood something.

Belive it or not, the Palm OS uses 16 bit addresses, it is quite
archaic. It makes programming a challenge. It makes one appreciate
CStrings in the Microsoft architecture.

?

>Allocate an array A of 300 pointers.

Could you share some code please?

char* pointers[300];

>Initialize the pointers to point to the strings.

Could you share some code please?

No, this smells like homework. Use a loop. If you have any problems,
post your code and describe exactly what the problem is.

I am a hobbiest programmer and char arrays have always been a challenge
for me.

--
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?