From: Garrett Mitchener <wgm2@acpub.duke.edu>
  To  : 
  Date: 28 Feb 1999 19:26:32 -0500

Re: getopt

Luke <lop@duke.edu> writes:

> I am having a little trouble understanding the getopt library
> implentation.
> 
> The specifications call for iterators and const iterators.  What is the
> difference?  I'm assuming we need something in the order of begin() and
> end() and operators ++ and * for incrementation and derefrencing,
> respectively, and a public iterator type so that users of the class can
> declare iterators.

When you do *plainIter, the value isn't const.  As in your iterator class
might look like this:

class FooIterator
{
public:
  Foo & operator *();
};

When you do *constIter, the value is const:

class ConstFooIterator
{
public:
  const Foo & operator *();
};


> Changing things so GetOpt uses strings and vectors shouldn't be too
> hard.  However, the C getopt has several static C variables that aren't
> really passed anywhere and just appear in the program, namely char
> *optarg and int optind.  This seems kinda sloppy for a
> C++ implementation.  I'm assuming converting the first to a static
> string, leaving the second as is, and just using it the same way that it
> would be in C is not a good idea??  Would it be better to pass an int
> and a string to getopt by reference and do it that way?

Global variables are just something you have to put up with in old C
code.  Your parser class may use them, but don't attempt to replace
them -- it won't work.  Your parser should also not just publicly
expose them.  It should be possible, if you wanted, to re-write your
parser to behave exactly the same way without calling getopt, and you
don't want global variables to be inherent in your design.

> My next question is about classes in this library.  The assignment makes
> it seem like we should have a lot of classes here- I can see having one
> for getopt and one for readenv, or something like that, but what else?
> I'm assuming we need to have sorters, but should we try to integrate
> them with the sorters in scandir?

Depending on how you design it, it can take from 2 to 64 classes to do
this assignment.  You should at least have a parser class, a scanner
class, various iterator classes, some means of filtering, and some
means of specifying a sort order.

> Also, is anyone else just a little frustrated that the link to
> usegetopt.cc doesn't work and this thing is due monday?
> 
> I am confused.  PLEASE HELP!!!
> -Luke

There is other getopt documentation available.  Look at the links on
the help page (call it up and search for getopt w/ netscapes find
command), and heed the warning about switch statements.

	-- garrett :-)