Re: maphash

[Greg Hill]

At 4:46 PM +0900 4/24/03, Stephen J. Turnbull wrote:
>  >>>>> "rms" == Richard Stallman <address@hidden> writes:
>
>     I have discovered by experimentation that maphash actually does what
>     I hoped it would, which is to pass key/value pairs to the mapping
>     function in the same order in which they were added to the table.
>
>     rms> An small anount of experimentation doesn't show you it will
>     rms> always to do that.  It would be necessary to study the code
>     rms> and construct a proof, before we could promise this to the
>     rms> users.
>
> If I understand the OP's description correctly, I can already promise
> you that code depending on such a feature won't be portable to XEmacs:
>
> (let ((my-hash (make-hash-table))
>       result)
>   (puthash "key1" "val1" my-hash)
>   (puthash "key2" "val2" my-hash)
>   (puthash "key3" "val3" my-hash)
>   (maphash (lambda (k v) (setq result (cons k result))) my-hash)
>   (reverse result))
>
> => ("key2" "key3" "key1")

Fortunately for me, in GNU Emacs Stephen's example--and several 
variations thereof--do work the way I described, and not the way they 
work in XEmacs.  Also, fortunately for me, my code does not have to 
be portable.


At 9:51 PM -0400 4/23/03, Richard Stallman wrote:
> Do you want to study the code?

After taking a quick look at the C source code, the simple answer to 
Richard's question is "No, thank you."  I do write code in C, when I 
absolutely have to, but I don't really care for the language.  And in 
general, I don't enjoy the challenge of figuring out how OP's code 
works, especially when it is written in C _and_ chock full of MACROs.

So, I'll just say: That's ok, I understand that you cannot, in good 
faith, make any promises either that this "feature" works relieably 
now, or even that if it happens to now, it always will.  It _is_ 
working for me reliably now, and I'll keep using it as long as it 
does; and I promise I won't complain if my decision to do so comes 
back to haunt me later on.

--Greg