Darren New wrote:
> Kevin Wampler wrote:
>> I don't know PHP, so I'm curious if you could elaborate a bit, since 
>> I'm used to viewing "dictionary" as more of less a synonym for 
>> "hashtable" in this context.
> 
> Hmmm... A dictionary in PHP is more like an array of key/value pairs. So 
> they preserve the order in which you inserted elements

Interesting.  So, to make sure I understand correctly if dicts in python 
were to operate like this then:

D = dict()
d["a"] = "foo"
d["b"] = "bar"
d["c"] = "baz"

would give me {"a":"foo", "b":"bar", "c":"baz"} where the order matters 
  so D[1] gives "bar"?

If so, then what happens in the following case:

D = dict()
d[3] = "foo"
d[2] = "bar"
d[1] = "baz"

or:

D = dict()
D[2000000000] = "foo"

I think any implementation which tries to behave both like a list and a 
hashtable is going to have some inconsistencies when using ints as keys, 
so I actually prefer the approach of keeping the two separate.  That 
said I do sometimes like the C++ stl approach of maintaining an ordering 
in a map based on the natural order of its elements.


> Honestly, I don't think I've ever *used* the fact that the keys maintain 
> an order even when they're not integers.

I actually have used this in python a few times, using a custom class 
rather than a straight dict of course.  Unfortunately I can't remember 
why I needed it.  I suspect it was so that I could pack the dict into a 
vector, perform some computations on it, and then put the results back 
into the dict.

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