[Top][All Lists]

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: maphash

From: Greg Hill
Subject: Re: maphash
Date: Thu, 24 Apr 2003 14:58:18 -0700

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))
  (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.


reply via email to

[Prev in Thread] Current Thread [Next in Thread]