hi,

there is a notice in the D reference, that this is not possible:

	int[] foo;
	int	i;

	foo[0] = 1;	
	foo[1] = 2;
	foo[2] = 3;
	foo[3] = 4;
	.
	.

	i = foo[3];

first, why causes this an error and second, why leads this into an error too:
	
	//XML is my class
	XML _xml;
	int i;	
	_xml = new XML(args[i]);

how could i program this without any arrayboundserror?

thx, alex

(p.s. sorry for my bad english.)
-- 
Using M2, Opera's revolutionary e-mail client: http://www.opera.com/m2/

alexander.panek wrote:
> hi,
> 
> there is a notice in the D reference, that this is not possible:
> 
>     int[] foo;

foo is 'null'

>     int    i;
> 
>     foo[0] = 1;   
 you cant do this as foo is null (foo.length == 0)

>     foo[1] = 2;
>     foo[2] = 3;
>     foo[3] = 4;
>     .
>     .
> 
>     i = foo[3];

try
foo.length = 4; (foo now has 4 elements). {0..3}
or
foo ~= 1;
foo ~= 2;
..etc..
you can ~= (append) to a null array


> 
> first, why causes this an error and second, why leads this into an error too:
>         //XML is my class
>     XML _xml;
>     int i;       _xml = new XML(args[i]);
> 
> how could i program this without any arrayboundserror?

set i to a value! did you want to pass an element of args or the whole array ?

> 
> thx, alex
> 
> (p.s. sorry for my bad english.)

Mike Wynn <mike@l8night.co.uk> wrote in news:bjg6lu$1164$1@digitaldaemon.com:

> alexander.panek wrote:
>> hi,
>> 
>> there is a notice in the D reference, that this is not possible:
>> 
>>     int[] foo;
> 
> foo is 'null'
> 
>>     int    i;
>> 
>>     foo[0] = 1;
>   you cant do this as foo is null (foo.length == 0)
> 
>>     foo[1] = 2;
>>     foo[2] = 3;
>>     foo[3] = 4;
>>     .
>>     .
>> 
>>     i = foo[3];
> 
> try
> foo.length = 4; (foo now has 4 elements). {0..3}
> or
> foo ~= 1;
> foo ~= 2;
> ..etc..
> you can ~= (append) to a null array

I think this won't work: Since foo is null you cannot append or resize it.

One could either create a static array:
     int[4] foo;
	int	i;

	foo[0] = 1;
	foo[1] = 2;
	foo[2] = 3;
	foo[3] = 4;


or use a dynamic array, that is initially empty (but not null).

     int[] foo=new int[0];
	int	i;

	foo ~= 1;
	foo ~= 2;
	foo ~= 3;
	foo ~= 4;

Farmer wrote:
> Mike Wynn <mike@l8night.co.uk> wrote in news:bjg6lu$1164$1@digitaldaemon.com:
> 
> 
>>alexander.panek wrote:
>>
>>>hi,
>>>
>>>there is a notice in the D reference, that this is not possible:
>>>
>>>    int[] foo;
>>
>>foo is 'null'
>>
>>
>>>    int    i;
>>>
>>>    foo[0] = 1;   
>>
>>  you cant do this as foo is null (foo.length == 0)
>>
>>
>>>    foo[1] = 2;
>>>    foo[2] = 3;
>>>    foo[3] = 4;
>>>    .
>>>    .
>>>
>>>    i = foo[3];
>>
>>try
>>foo.length = 4; (foo now has 4 elements). {0..3}
>>or
>>foo ~= 1;
>>foo ~= 2;
>>..etc..
>>you can ~= (append) to a null array
> 
> 
> I think this won't work: Since foo is null you cannot append or resize it.
> 
> or use a dynamic array, that is initially empty (but not null).
> 
>      int[] foo=new int[0];
> 	int	i;
> 
> 	foo ~= 1;	
> 	foo ~= 2;
> 	foo ~= 3;
> 	foo ~= 4;
> 

have you tried;
int[] foo;
foo ~= 1;

or even foo = new int[0];
if ( foo === null ) { printf( "foo is null"); }

just try ......

import c.stdio;

int main( char[][] args ) {
	int[] foo;
	int[] bar;
	foo = null; // force null;
	foo ~= 1;
	printf( "foo.length=%d\n", foo.length );
	printf( "foo[0] = %d\n", foo[0] );
	bar = new int[0];
	if ( bar === null ) { printf( "bar is null\n"); }
	return 0;
}

--------
on linux I get
foo.length=1
foo[0] = 1
bar is null

(the same as I used to get on windows)
if your going to post at least try out some code!

"Mike Wynn" <mike@l8night.co.uk> wrote in message
news:bjiu9j$207p$1@digitaldaemon.com...
| if your going to post at least try out some code!
|

At least lately (one week, maybe two) we haven't had any C++ code.
I agree with Mike: when we post code ideas we should try to do it in D, or
some sort of pseudo D at least. It'll even help yourselves: you'll become
familiar with, and if you make any mistakes, maybe someone will correct it.
Also, when new people come they'll see more D code and will notice we're
using it.
Also, it's good to try to give a "D flavour" to the code. eg: Daniel said it
was better to use ~= instead of += in I-don't-remember-exactly-what-post.
Also ("also" day for me :) ) try the compiler: "does D support this? does D
support that?". Try it! (no offence intended)

-------------------------
Carlos Santander
"Mike Wynn" <mike@l8night.co.uk> wrote in message
news:bjiu9j$207p$1@digitaldaemon.com...
| if your going to post at least try out some code!
|

At least lately (one week, maybe two) we haven't had any C++ code.
I agree with Mike: when we post code ideas we should try to do it in D, or
some sort of pseudo D at least. It'll even help yourselves: you'll become
familiar with, and if you make any mistakes, maybe someone will correct it.
Also, when new people come they'll see more D code and will notice we're
using it.
Also, it's good to try to give a "D flavour" to the code. eg: Daniel said it
was better to use ~= instead of += in I-don't-remember-exactly-what-post.
Also ("also" day for me :) ) try the compiler: "does D support this? does D
support that?". Try it! (no offence intended)

-------------------------
Carlos Santander

Mike Wynn <mike@l8night.co.uk> wrote in news:bjiu9j$207p$1@digitaldaemon.com:

> if your going to post at least try out some code!
> 

I'm sorry, I had better done so.

You're right, your code works fine.


DMD doesn't care whether you write
   int[] foo = new int[0];
or
   int[] foo;
Both produces the same code (even if optimization is turned off).



I'm not happy with the current situation:
1)I can't distinguish between an empty array and a null array. Which is
sometimes handy.


2)Arrays/Slices seem a bit erratic with regard to beeing null or empty. Here's an example:

void main()
{
   int[] foo = new int[0];
   if (foo === null) printf("foo is null\n");

   int[] foo2 = new int[1];
   int[] emptySlice = foo2[0..0];

   if (emptySlice !== null) printf("emptySlice is NOT null\n");

   emptySlice.length = 0;
   if (emptySlice === null) printf("emptySlice is now null\n");
}

prints:

foo is null
emptySlice is NOT null
emptySlice is now null