GNU Data Language (GDL) is a free IDL (Interactive Data Language)
 compatible incremental compiler. It has full syntax compatibility
 with IDL 7.1. IDL is a registered trademark of ITT Visual Information
 Solutions. From IDL 8.0, the following language elements are
 supported:
 .
  * FOREACH loop
  * negative array indices
  * garbage collection pointers and objects
  * call methods on an object using "." (e. g. `object.aMemberProcedure,arg1`)
 .
 The file input output system is fully implemented. GUI support (widgets) is
 officially provided, but it's not complete yet.
 .
 This package contains the main commandline and interpreter frontend.