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IDL-Fortran String/Char Passing [message #1057]

Tue, 15 June 1993 12:01

wicker
Messages: 2
Registered: June 1993

Junior Member

Hi there. We are doing some idl development which is using some fortran
routines. Does anyone out there know how to pass character data from idl
to fortran and vice versa? I know how to do integer and real data, no
problem. Examples of working code would be VERY welcome.

Also, anybody else notice that the new HDF interface in IDL is REALLY slow
as compared to C or Fortran.

Thanks in advance.

| |
| Prof. Louis Wicker email: wicker@ariel.tamu.edu |
| TAMU/Meteorology Dept phone: (409) 845 - 8084 |
| 1204 Eller O&M Bld fax: (409) 826 - 4466 |
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Re: IDL-Fortran String/Char Passing [message #1250 is a reply to message #1057]

Wed, 16 June 1993 09:41

Bill Davis
Messages: 4
Registered: June 1993

Junior Member

In article <wicker-150693135755@wicker.tamu.edu> Dr. Louis J. Wicker,
wicker@ariel.tamu.edu writes:
> Hi there. We are doing some idl development which is using some fortran
> routines. Does anyone out there know how to pass character data from idl
> to fortran and vice versa? I know how to do integer and real data, no
> problem. Examples of working code would be VERY welcome.

I do it under VMS. Read all about CALL_EXTERNAL in the User's Guide and
Reference Manual. Passing characters into a FORTRAN routine is no
problem. I must say that it was not trivial to implement returning
strings even after reading the manual. I feel something like the
following example should be included in the documentation:

VMS FORTRAN routine to return a string variable via IDL CALL_EXTERNAL:

INTEGER* 4 FUNCTION retstring ! address pointer is
returned

CHARACTER*16 local_string
CHARACTER*1 null
DATA null /'00'X/

local_string = 'new stuff'//null ! Concatenate null
terminator
retstring = %LOC(local_string) ! Return address of string

RETURN
END

This routine is put into a VMS shared image which is pointed to by the
logical name MY_IMAGE (also non-trivial if you have never done it). Then
in IDL:

strvar=CALL_EXTERNAL(/S_VALUE,'MY_IMAGE','RETSTRING')

This is painfull if you have more than 1 string variable (I believe you
will need one routine per string variable). You may wish to see if using
LINKIMAGE would be easier.

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