From: Hal Fulton <hal9000@...>
Date: 2004-09-06T08:41:25+09:00
Subject: Re: Hashes and ordering

Markus wrote:

> Here's a stab at an instance of case #1, the simplest way I could come
> up with to model the semantics I think you are looking for (note: this
> is _not_ claimed to be the best way to implement the semantics, just the
> clearest way to express them):

[snip code]

Yes, I have implemented things similar to this before. The one remaining
problem for me was always a convenient syntax for literals. (It may not
be so important to most people, but it is to me.)

> This setup gives the following answers to the questions I'd asked
> previously (properly translated of course):
> 
> p _(1=>2)+_(3=>4)            # _(1=>2)+_(3=>4)
> 
> p _(1=>2)+_(3=>4)+_(1=>5)    # _(3=>4)+_(1=>5)

[snip rest of examples]

Your underscore notation is clever, but compared to traditional hash
notation it still hurts my eyes (and my fingers).

As for semantics, I think you have captured my intent, although I
may have missed one or two items.

I will certainly save this for my notes also.

However, Matz's latest reply indicates to me that if order is added
to the Hash class, then even literals will be ordered.

I had thought that ordered literals would imply that

   {a=>b,c=>d} != {c=>d,a=>b}

but I see now that is not the case.



Thanks,
Hal