| Re: LIST extensions [message #73962] |
Tue, 14 December 2010 22:51  |
Matt Haffner
Messages: 34
Registered: October 2000
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Member |
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On Dec 14, 3:51 pm, Paul van Delst <paul.vande...@noaa.gov> wrote:
> Hello,
>
> Sorry to keep flogging this particular topic, but I'm currently up to my eyes in adapting some code from using pointers
> to using lists (partly for curiosity, partly to avoid nested pointer dereferencing), and I've found the very simple
> methods below to be useful in dealing with the "is it empty?", "are there nulls in the list?" etc type of questions I've
> been asking here.
>
> Comments?
>
> cheers,
>
> paulv
>
> ;+
> ; NAME:
> ; List::Empty
> ;
> ; PURPOSE:
> ; The List::Empty function method return TRUE if a list contains
> ; no elements, FALSE otherwise.
> ;
> ; CALLING SEQUENCE:
> ; result = Obj->[List::]Empty()
> ;-
> FUNCTION List::Empty
> RETURN, N_ELEMENTS(self) EQ 0
> END
>
> ;+
> ; NAME:
> ; List::Length
> ;
> ; PURPOSE:
> ; The List::Length function method returns the number of
> ; elements in a list.
> ;
> ; CALLING SEQUENCE:
> ; result = Obj->[List::]Length()
> ;-
> FUNCTION List::Length
> RETURN, N_ELEMENTS(self)
> END
>
> ;+
> ; NAME:
> ; List::n_Items
> ;
> ; PURPOSE:
> ; The List::n_Items function method returns the number of
> ; non-null elements in a list.
> ;
> ; CALLING SEQUENCE:
> ; result = Obj->[List::]n_Items()
> ;-
> FUNCTION List::n_Items
> idx = WHERE(self NE !NULL, count)
> RETURN, count
> END
>
> ;+
> ; NAME:
> ; List::Compact
> ;
> ; PURPOSE:
> ; The List::Compact function method returns a copy of a list
> ; with all null elements removed.
> ;
> ; CALLING SEQUENCE:
> ; result = Obj->[List::]Compact()
> ;-
> FUNCTION List::Compact
> idx = WHERE(self NE !NULL, count)
> RETURN, ( count GT 0 ) ? self[idx] : LIST()
> END
Useful--thanks.
Also, note that LIST is a subclass of IDL_Container, which has
a .Count() method, so .Length() may not be needed. There is also
a .Move method to rearrange items in a container. Unfortunately
the .IsContained method doesn't seem to work for me on a LIST though
(and is only for objects, in any case):
IDL> z=g[50]
IDL> print,g.IsContained(z)
0
IDL> print,obj_valid(z, /get_heap)
1884104
IDL> print,obj_valid(g[50], /get_heap)
1884104
IDL> print, z eq g[50]
1
mh
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