Function:   gds___fail

Purpose:    verify condition and handle error when condition not met.

Author:     J.P. Terlouw
 
Category:   BASIC-GDS

File:       gdsd_basic.c

Use:        int gds___fail(int verify, fint erri, fint *erro)
            
            It is similar to GDS___CHECK.
            
            If "error" is present and is negative due to a previous
            error condition, 1000 is subtracted from it to indicate
            failure in a previous call and gds___error_c is called
            with this value. This causes the program to abort with
            an error message.
            
            If "verify" is true, gds___fail returns false.
            
            If "verify" is false, then the presence of "erro" is checked.
            If it is present, then "erri" is copied to "erro" and true is
            returned.
            If it is not present, then gds___error_c is called with "erri"
            as argument.

Updates:   21-Dec-89   --  original document