Re: dlm creating an array?

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

Thanks for the help JD and Jim!  That was WAY easier than I thought it
would be :)

Randall

> Two ways.  Here is the better:
> 
> void test_array(int argc, IDL_VPTR argv[])
> {
>   float *test;
>   int i;
>   IDL_MEMINT dim[2];
>   IDL_VPTR tmp;
> 
>   dim[0]=dim[1]=10;
>   /* Make Sure we can write to it, free anything already associated */
>   IDL_StoreScalarZero(argv[0], IDL_TYP_LONG);
> 
>   test=(float *)IDL_MakeTempArray(IDL_TYP_FLOAT,
> 2,dim,IDL_ARR_INI_NOP,&tmp);
>   IDL_VarCopy(tmp,argv[0]); /* This is the key.  Copy tmp to passed arg
> */
>   for(i=0;i<100;i++) test[i]=i*i;
> }
> 
> That is, you make a temporary array, and copy it over to the passed
> argument (no data is actually copied, since it's a temporary).  The
> StoreScalarZero makes sure it's passed by reference. 
> 
> This method is easiest.  Another way is to make your own data, and then
> use IDL_Import_Array to wrap an IDL_VPTR around it (also no copying
> performed).  They are basically equivalent, but the typing is more up
> front with a the temporary variable method.  
> 
> Please note that I did not free the tmp VPTR with IDL_DelTmp().  Why? 
> Because it was already reclaimed by IDL_VarCopy (which in this case is
> more of a renaming than a copy).  Doing so twice is a no-no.
> 
> What if you have an arbitrary number of dimensions (read from the file
> perhaps)?  I'd simply declare dim[IDL_MAX_ARRAY_DIM] instead, and test
> to ensure this limit isn't surpassed.
> 
> Good luck,
> 
> JD
>