Function:     irds_exist

Purpose:      To test whether a gipsy set is a legal irds.

Category:     IR

File:         irds_basic.c

Author:       P.R. Roelfsema

Use:          INTEGER IRDS_EXIST( IRDS ,       Input   character*(*)
                                  ERROR  )     Output  integer

              IRDS_EXIST  Returns code to indicate what IRDS is"
                           0  - irds is a legal IR data structure.
                          -1  - irds does not exist.
                          -2  - irds exists but has wrong dimension
                          -3  - irds has no sample axis
                          -4  - irds has no tick axis
                          -5  - irds has no detector axis
                          -6  - irds has no snip axis
              IRDS        name of irds.
              ERROR       gds error code.

Updates:      Aug 10, 1990: PRR, Creation date
	      Feb 19, 1992: DK, make ERROR indeed an output param ONLY