Properly Initializing a Dynamically Defined Triple String Array?

[sherman]

string ***dat_array;
int t;

dat_array = new string **[t];
for (i=0; i<t; i++) {
dat_array[i] = new string *[3];
for (j=0; j<5; j++)
dat_array[i][j] = new string [5];
}
// dat_array = new string **[t];
for (i=0; i<t; i++)
for (j=0; j<3; j++)
for (k=0; k<5; k++)
dat_array[i][j][k] = string("Hello Everybody!");

@@@@@@@@@@@@@@@ @@@@@@

Is this the proper way to initialize a dynamically defined triple
string array "dat_array[t][3][5]"? I know a priori the last two
dimensions. I get the fist one, t , later in the program.
Thank you.

sherman

[Paavo Helde]

Re: Properly Initializing a Dynamically Defined Triple String Array?

sherman kirjutas:

string ***dat_array;
int t;
>
dat_array = new string **[t];
for (i=0; i<t; i++) {
dat_array[i] = new string *[3];
for (j=0; j<5; j++)
dat_array[i][j] = new string [5];
}
// dat_array = new string **[t];
for (i=0; i<t; i++)
for (j=0; j<3; j++)
for (k=0; k<5; k++)
dat_array[i][j][k] = string("Hello Everybody!");
>
@@@@@@@@@@@@@@@ @@@@@@
>
Is this the proper way to initialize a dynamically defined triple
string array "dat_array[t][3][5]"? I know a priori the last two
dimensions. I get the fist one, t , later in the program.

Seems to be technically correct, but tedious and error-prone. I would
probably use something like the following:

int idx(int i, int j, int k, int t) {
return i + j*t + k*t*3;
}

std::vector<std ::stringdat_arr ay;
dat_array.resiz e( t*3*5);
....
dat_array[idx(i, j, k, t)] = "Hello everybody!";

YMMV
Paavo

[red floyd]

Re: Properly Initializing a Dynamically Defined Triple String Array?

Paavo Helde wrote:

sherman kirjutas:
>

>string ***dat_array;
>int t;
>>
> dat_array = new string **[t];
> for (i=0; i<t; i++) {
> dat_array[i] = new string *[3];
> for (j=0; j<5; j++)
> dat_array[i][j] = new string [5];
> }
>// dat_array = new string **[t];
> for (i=0; i<t; i++)
> for (j=0; j<3; j++)
> for (k=0; k<5; k++)
> dat_array[i][j][k] = string("Hello Everybody!");
>>
>@@@@@@@@@@@@@@ @@@@@@@
>>
>Is this the proper way to initialize a dynamically defined triple
>string array "dat_array[t][3][5]"? I know a priori the last two
>dimensions. I get the fist one, t , later in the program.

>
Seems to be technically correct, but tedious and error-prone. I would
probably use something like the following:
>
int idx(int i, int j, int k, int t) {
return i + j*t + k*t*3;
}
>
std::vector<std ::stringdat_arr ay;
dat_array.resiz e( t*3*5);
...
dat_array[idx(i, j, k, t)] = "Hello everybody!";
>

If you're going to do it that way, I'd wrap dat_array in a class, and
provide operator()(int, int, int)

[Paavo Helde]

Re: Properly Initializing a Dynamically Defined Triple String Array?

red floyd <no.spam.here@e xample.comkirju tas:

Paavo Helde wrote:

>sherman kirjutas:
>>

>>string ***dat_array;
>>int t;
>>>
>> dat_array = new string **[t];
>> for (i=0; i<t; i++) {
>> dat_array[i] = new string *[3];
>> for (j=0; j<5; j++)
>> dat_array[i][j] = new string [5];
>> }
>>// dat_array = new string **[t];
>> for (i=0; i<t; i++)
>> for (j=0; j<3; j++)
>> for (k=0; k<5; k++)
>> dat_array[i][j][k] = string("Hello Everybody!");
>>>
>>@@@@@@@@@@@@@ @@@@@@@@
>>>
>>Is this the proper way to initialize a dynamically defined triple
>>string array "dat_array[t][3][5]"? I know a priori the last two
>>dimensions. I get the fist one, t , later in the program.

>>
>Seems to be technically correct, but tedious and error-prone. I would
>probably use something like the following:
>>
>int idx(int i, int j, int k, int t) {
> return i + j*t + k*t*3;
>}
>>
>std::vector<st d::stringdat_ar ray;
>dat_array.resi ze( t*3*5);
>...
>dat_array[idx(i, j, k, t)] = "Hello everybody!";
>>

>
If you're going to do it that way, I'd wrap dat_array in a class, and
provide operator()(int, int, int)

Yes, by encapsulating and abstracting one can build tools exactly
matching the needs. Another question is whether it requires a lot of
boilerplate code, and whether it is worth it. std::vector has a rich
interface, and I would not like to lose it. For example, the deeply
nested loop for initialization with the same value in the OP post could
be replaced by a single line:

std::fill( dat_array.begin (), dat_array.end() , "Hello Everybody!");

So either one should derive publicly from std::vector (which creates its
own problems), or write some forwarding boilerplate code. Maybe the right
approach would be to derive privately from std::vector and add using
declarations for all needed names.

Paavo