Re: A question to all you DLM experts...

[Randall Skelton <rhskelto(at)atm.ox.ac.uk>]

Thanks to Jim, who pointed out that 10*2 is 20 not 100.

i.e. 'for i=0; i<100; i++' should be 'for i=0; i<dim[0]*dim[1]; i++'

I hate it when I do that...

Cheers,
Randall

On Sat, 9 Jun 2001, Randall Skelton wrote:

> Hi all,
> 
> There is something subtle that I'm missing here... I have a trivial DLM
> called 'array from nothing' because it is supposed to create an array in C
> using IDL temporary memory and then return it to IDL using VarCopy.  The
> problem is, when I initially define my new array, it works fine, but that
> variable name seems to be defunct for re-assignment?  What exactly does,
> 'Array has a corrupted descriptor' mean?
> 
> -------------
> IDL> ok=arrayfromnothing(a)
> % Loaded DLM: MYIDL.
> IDL> print, a
>       0.00000      1.00000      4.00000      9.00000      16.0000
>       25.0000      36.0000      49.0000      64.0000      81.0000
>       100.000      121.000      144.000      169.000      196.000
>       225.000      256.000      289.000      324.000      361.000
> IDL> help, a
> A               FLOAT     = Array[10, 2]
> IDL> a=fltarr(10,2)
> % Array has a corrupted descriptor: A.
> % Execution halted at:  $MAIN$                 
> IDL> help, a
> A               UNDEFINED = <Undefined>
> -------------
> 
> Below is the DLM code.  Any comments?
> 
> Cheers,
> Randall
> 
> -------------
> /* function: arrayFromNothing */
> IDL_VPTR IDL_CDECL arrayFromNothing(int argc,
>                     IDL_VPTR argv[], char *argk) {
>     /* Called in IDL as:
>      *     ret = arrayFromNothing(new_array)
>      */
>   
>     /* general index */
>     int i;
>     
>     /* local pointer */
>     float *ptr;
>     
>     /* IDL specific */
>     IDL_MEMINT dim[2];   
>     IDL_VPTR tmp;
>              
>     /* set the correct dimension for the new array */
>     dim[0]=10; 
>     dim[1]=2;
>              
>     /* Make Sure we can write to it, free anything already associated */
>     IDL_StoreScalarZero(argv[0], IDL_TYP_FLOAT);
>     
>     /* make a temporary IDL array with the same memory address as ptr */
>     ptr=(float *)IDL_MakeTempArray(IDL_TYP_FLOAT,2,dim,IDL_ARR_INI_ZERO,&tmp);
>     
>     /* fill the array */
>     for(i=0;i<100;i++) ptr[i]=i*i;
>     
>     /* copy the IDL_VPTR tmp to passed arg */
>     IDL_VarCopy(tmp,argv[0]);
>     
>     /* return 1 signifying no errors in execution */
>     return (IDL_GettmpLong(1));
> }
> 
>