Re: Is STL iterator singleton ?

 James Kanze <>
Wed, 08 Aug 2007 12:13:00 -0000
On Aug 8, 11:05 am, Erik Wikstr=F6m <> wrote:

On 2007-08-08 06:00, raan wrote:

Is iterators singleton?

I am accessing a map through wrapper functions to it; that
allow me to access the contents of the map as

CUnit &unit = hash.getFirstunit();
    unit = hash.getNextUnit();

Thats all about it. A call to getFirstUnit will initialize
the iterator. hasMoreUnits will move the iterator one unit
forward and hasNextUnit will access the next one and so on.

To answer the question in the subject, no.

What I really want to know is how you implemented that wrapper
to get that kind of functionality, using global variables? My
advice, if you insist on keeping the code like that, is to
make hasMoreUnits() and getNextUnit() take a CUnit as
parameter so they know which iterator to test for end /

My advice is to not use that interface. It's probably the
poorest solution to the question of how to iterate over all of
the elements.

If the problem you are trying to solve is to iterate over your
home-made hashmap then perhaps you should instead you should
try to create a STL- compatible iterator (i.e. one that
behaves like other iterators). I've done it, so it's quite

Creating a classical iterator, such as described in the GoF, is
generally even easier, and it's easier to use. I try to provide
both interfaces to my iterators; I'll use the STL interface when
calling standard algorithms (or rather, the standard algorithms
will use the STL interface), and the GoF interface most of the
rest of the time (since it only requires a single iterator
object, instead of two).

James Kanze (GABI Software)
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