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UNDEFINE

UNDEFINE

Name


      UNDEFINE

Purpose


      The purpose of this program is to delete or undefine
      an IDL program variable from within an IDL program or
      at the IDL command line. It is a more powerful DELVAR.
      Pointer and structure variables are traversed recursively
      to undefine any variables pointed to in the pointer or in
      a structure dereference.

Author


      FANNING SOFTWARE CONSULTING
      David Fanning, Ph.D.
      1642 Sheely Drive
      Fort Collins, CO 80526 USA
      Phone: 970-221-0438
      E-mail: david@idlcoyote.com
      Coyote's Guide to IDL Programming: http://www.idlcoyote.com

Category


      Utilities.

Calling Sequence


      UNDEFINE, variable

Required Inputs


      variable: The variable to be deleted. Up to 10 variables may be specified as arguments.

Side Effects


      The variable no longer exists.

Example


      To delete the variable "info", type:
        IDL> Undefine, info
       
        IDL> var = ptr_new({a:ptr_New(5), b:findgen(11), c: {d:ptr_New(10), f:findgen(11)}})
        IDL> Help, /Heap
        Heap Variables:
            # Pointer: 3
            # Object : 0
        <PtrHeapVar3> LONG = 5
        <PtrHeapVar4> LONG = 10
        <PtrHeapVar5> STRUCT = -> Array[1]
       
        IDL> Undefine, var
        IDL> Help, /Heap
        Heap Variables:
            # Pointer: 0
            # Object : 0
        IDL> Help, var
        VAR UNDEFINED = <Undefined>

Modification History


      Written by David W. Fanning, 8 June 97, from an original program
      given to me by Andrew Cool, DSTO, Adelaide, Australia.
      Simplified program so you can pass it an undefined variable. :-) 17 May 2000. DWF
      Simplified it even more by removing the unnecessary SIZE function. 28 June 2002. DWF.
      Added capability to delete up to 10 variables at suggestion of Craig Markwardt. 10 Jan 2008. DWF.
      If the variable is a pointer, object or structure reference the variable is recursively traversed
          to free up all variables pointed to before the variable is itself destroyed. 10 June 2009. DWF.
      Updated to allow undefining of pointer arrays. 8 October 2009. DWF.
      Valid pointers that point to undefined variable can cause an infinite loop. Now using
          Heap_Free, rather than recursion, with pointers. 30 May 2013. DWF.



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