[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: Undocumented array indexing feature?
- Subject: Re: Undocumented array indexing feature?
- From: "J.D. Smith" <jdsmith(at)astrosun.tn.cornell.edu>
- Date: Fri, 22 Jan 1999 17:28:54 +0000
- Newsgroups: comp.lang.idl-pvwave
- Organization: Cornell University
- References: <36A792FF.DA5E1E31@ssec.wisc.edu> <36A8962D.428A16D5@ssec.wisc.edu>
- Sender: jts11(at)cornell.edu (Verified)
- Xref: news.doit.wisc.edu comp.lang.idl-pvwave:13406
Liam Gumley wrote:
> Liam Gumley wrote:
> > Here's a way to index an array I hadn't seen before:
> > a = indgen(10,10)
> > x = [3,5,8,9]
> > y = [2,7]
> > print, (a[x,*])[*,y]
> > 23 25 28 29
> > 73 75 78 79
> > Does anyone know where this feature (i.e. enclosing an array with
> > parentheses and appending an index) is documented? I couldn't find it in
> > my printed IDL 5.0 documentation.
> To answer my own question, a careful reading of Chapter 5 of 'Building
> IDL Applications' p. 60
> revealed the following:
> "The syntax of a subscript reference is:
> Variable_Name[Subscript_ List]
> Thanks to Bill and Craig for their replies.
Array indexing isn't the only place parentheses are useful...
try this sometime:
Basically, parentheses just instruct the command parser to iterate as
many times as necessary to remove them all. Other examples:
It doesn't work for everything though... as evidenced by:
J.D. Smith |*| WORK: (607) 255-5842
Cornell University Dept. of Astronomy |*| (607) 255-6263
304 Space Sciences Bldg. |*| FAX: (607) 255-5875
Ithaca, NY 14853 |*|