How do we get dynamic memory in D ?

I want to use memory based on user input. In this case declare a bi-dimensional array (int[2][var]), var being the user input.

On Friday, 24 July 2015 at 15:22:15 UTC, Binarydepth wrote:
> I want to use memory based on user input. In this case declare a bi-dimensional array (int[2][var]), var being the user input.

Declare:

int[2][] your_array;

your_array.length = var;


The runtime will handle the dynamic memory allocation for you when you set the length on a slice.

On Friday, 24 July 2015 at 15:26:27 UTC, Adam D. Ruppe wrote:
> On Friday, 24 July 2015 at 15:22:15 UTC, Binarydepth wrote:
>> I want to use memory based on user input. In this case declare a bi-dimensional array (int[2][var]), var being the user input.
>
> Declare:
>
> int[2][] your_array;
>
> your_array.length = var;
>
>
> The runtime will handle the dynamic memory allocation for you when you set the length on a slice.

this is what I did :

int liCases [2][];
        readf(" %d\n", &num);//Number of cases input
        liCases.length = num;

And I get this error :

prime1.d:26: error: constant liCases.length is not an lvalue

On Friday, 24 July 2015 at 15:26:27 UTC, Adam D. Ruppe wrote:
> On Friday, 24 July 2015 at 15:22:15 UTC, Binarydepth wrote:
>> I want to use memory based on user input. In this case declare a bi-dimensional array (int[2][var]), var being the user input.
>
> Declare:
>
> int[2][] your_array;
>
> your_array.length = var;
>
>
> The runtime will handle the dynamic memory allocation for you when you set the length on a slice.

Ok, Sorry I was declaring the array in C style also. It compiled after chaging it. :D

TY

On Friday, 24 July 2015 at 15:33:45 UTC, Binarydepth wrote:
> int liCases [2][];

Those brackets are in the wrong place, you should write that as

int[2][] liCases;


The syntax you used there is a deprecated C compatibility feature. in C, arrays are defined differently and the dimensions go in the opposite direction than in D. (So int a[2][] in C means int[][2] in D - that's why the length doesn't change in that format.)

But write it the D style for most consistency and it will work out. Just be aware that what I wrote is a dynamic array of two elements, not a two element group of dynamic arrays. So indexing is

liCases[i][0] and liCases[i][1] rather than swapping those.

Here is what I'm trying to do :

import std.stdio : readf, writef;
void main()	{
	int[2][] nam;
	int num;
	readf(" %d", &num);
	nam.length = num;
	foreach(nim; 0..num)	{
		readf(" %d %d", &nam[0][num], &nam[1][num]);
	}
	foreach(nim; 0..num)	{
		writef(" %d %d\n", &nam[0][num], &nam[1][num]);
	}
}

And here is the output I get when running the program :

core.exception.RangeError@code.d(8): Range violation
----------------
0x406cfb _Dmain
	???:0
0x415fde void rt.dmain2._d_run_main(int, char**, extern (C) int function(char[][])*).runAll().void __lambda1()
	../../../../src/libphobos/libdruntime/rt/dmain2.d:408
0x41624e void rt.dmain2._d_run_main(int, char**, extern (C) int function(char[][])*).tryExec(scope void delegate())
	../../../../src/libphobos/libdruntime/rt/dmain2.d:383
0x4164a8 void rt.dmain2._d_run_main(int, char**, extern (C) int function(char[][])*).runAll()
	../../../../src/libphobos/libdruntime/rt/dmain2.d:408
0x41624e void rt.dmain2._d_run_main(int, char**, extern (C) int function(char[][])*).tryExec(scope void delegate())
	../../../../src/libphobos/libdruntime/rt/dmain2.d:383
0x4163d5 _d_run_main
	../../../../src/libphobos/libdruntime/rt/dmain2.d:416
0x7f51eb84ea3f __libc_start_main
	???:0
0x406088 _start
	???:0
0xffffffffffffffff ???
	???:0
----------------------------------------------------------------------------------

I just want to read and print data depending on user input.

On Tuesday, 28 July 2015 at 16:09:46 UTC, Binarydepth wrote:
> 		readf(" %d %d", &nam[0][num], &nam[1][num]);
> 	}
> 	foreach(nim; 0..num)	{
> 		writef(" %d %d\n", &nam[0][num], &nam[1][num]);

Those indexes are backwards. And you really shouldn't need & on write. so try:

 		readf(" %d %d", &nam[num][0], &nam[num][1]);

and

 		writef(" %d %d\n", nam[num][0], nam[num][1]);

On Tuesday, 28 July 2015 at 16:12:28 UTC, Adam D. Ruppe wrote:
> On Tuesday, 28 July 2015 at 16:09:46 UTC, Binarydepth wrote:
>> 		readf(" %d %d", &nam[0][num], &nam[1][num]);
>> 	}
>> 	foreach(nim; 0..num)	{
>> 		writef(" %d %d\n", &nam[0][num], &nam[1][num]);
>
> Those indexes are backwards. And you really shouldn't need & on write. so try:
>
>  		readf(" %d %d", &nam[num][0], &nam[num][1]);
>
> and
>
>  		writef(" %d %d\n", nam[num][0], nam[num][1]);

I declared : int[2][] nam;

For real it is backwards ? nam[0][num]

On Tuesday, 28 July 2015 at 16:09:46 UTC, Binarydepth wrote:
> Here is what I'm trying to do :
>
> import std.stdio : readf, writef;
> void main()	{
> 	int[2][] nam;
> 	int num;
> 	readf(" %d", &num);
> 	nam.length = num;
> 	foreach(nim; 0..num)	{
> 		readf(" %d %d", &nam[0][num], &nam[1][num]);
> 	}
> 	foreach(nim; 0..num)	{
> 		writef(" %d %d\n", &nam[0][num], &nam[1][num]);
> 	}
> }


In addition to Adam:
there are typos (num instead of nim) - since num is the array length and the indices are 0-based, num is out of bounds...

	foreach(nim; 0..num)	{
		readf(" %d %d", &nam[nim][0], &nam[nim][1]);
	}
	foreach(nim; 0..num)	{
		writef(" %d %d\n", nam[nim][0], nam[nim][1]);
	}
works fine.

On Tuesday, 28 July 2015 at 16:24:39 UTC, anonymous wrote:
> On Tuesday, 28 July 2015 at 16:09:46 UTC, Binarydepth wrote:
>> Here is what I'm trying to do :
>>
>> import std.stdio : readf, writef;
>> void main()	{
>> 	int[2][] nam;
>> 	int num;
>> 	readf(" %d", &num);
>> 	nam.length = num;
>> 	foreach(nim; 0..num)	{
>> 		readf(" %d %d", &nam[0][num], &nam[1][num]);
>> 	}
>> 	foreach(nim; 0..num)	{
>> 		writef(" %d %d\n", &nam[0][num], &nam[1][num]);
>> 	}
>> }
>
>
> In addition to Adam:
> there are typos (num instead of nim) - since num is the array length and the indices are 0-based, num is out of bounds...
>
> 	foreach(nim; 0..num)	{
> 		readf(" %d %d", &nam[nim][0], &nam[nim][1]);
> 	}
> 	foreach(nim; 0..num)	{
> 		writef(" %d %d\n", nam[nim][0], nam[nim][1]);
> 	}
> works fine.

Damn! my first typo! Thanks :D