| Re: callable IDL and structures [message #30076 is a reply to message #30074] |
Mon, 08 April 2002 13:13   |
Sebastian Moeller
Messages: 7
Registered: April 2002
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Junior Member |
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Hello Mr. Fanning
this really is a nice and impressivly quick news group. Thank you very
much for answering.
David Fanning wrote:
[schnipp]
> Yes, this is correct (on both counts). Ten minutes of looking
> through on-line help doesn't come up with anything, but I know
> it is documented *somewhere*. This is an alternative way to
> access the fields of a structure. But if they are available
> this way, they are sure as heck available via the fields names
> as well. I'd like to see the code you are using to "access" them
> by their names.
[schnapp]
OK, here we go... This is the part in the C++ project. It is supposed to
define the named structure str
typedef
struct
{
int testarr[50];
int field2;
} teststr;
IDL_MEMINT d1[10];
d1[0]=1;
d1[1]=50;
IDL_STRUCT_TAG_DEF sd[4];
sd[0].name="testarr";
sd[0].type=(void*)IDL_TYP_LONG;
sd[0].dims=(IDL_MEMINT*)d1;
sd[0].flags=NULL;
sd[1].name="field2";
sd[1].type=(void*)IDL_TYP_LONG;
sd[1].dims=NULL;
sd[1].flags=NULL;
sd[2].name=NULL;
sd[2].type=NULL;
sd[2].dims=NULL;
sd[2].flags=NULL;
IDL_MEMINT d[3];
d[0]=1;
for(int k=0; k<50; k++)
{
teststr.testarr[k]=k;
}
teststr.field2=10;
void* ss=IDL_MakeStruct("str",sd);
var=IDL_ImportNamedArray("teststr",1,d,IDL_TYP_STRUCT,(UCHAR*)(&teststr),0,ss);
int err=IDL_ExecuteStr("help, /structure, teststr");
/* this line gives the whole information for the structure, including
the tag names and tag types as defined in this c fragment (teststarr and
field2). Also the data contained in the structure (the array containing
the subscript values and 10 for field2) is shown correctly.*/
err=IDL_ExecuteStr("print, teststr.field2");
/*this line gives an error message about field2 not beeing defined in
teststr, even thoug the preceedind command showed that teststr contained
the tags testarr and field2*/
err=IDL_ExecuteStr("print, teststr.(where(TAG_NAMES(teststr) EQ 'testarr'))");
/*this line actually works, it prints the content of the array (numbers
from 0 to 49). It is a rude attempt to bring the structure tag names
back into the game, and a pretty obfusceted way to write "print,
teststr.(0)". A few defines along the lines of: #define testarr (0),
would save the day...*/
To sum it up we are able to pass the data to IDL. And IDL has all the
meta-information about the structure's contents (tags, types and data).
The tag names can even be seen from the TAG_NAMES function, but attempts
to address the tags directly fail.
I hope this information serves to illustrate the problem more deeply.
Ahoi
Sebastian Moeller
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