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Re: Merging guix.el

From: Ludovic Courtès
Subject: Re: Merging guix.el
Date: Sun, 31 Aug 2014 16:59:38 +0200
User-agent: Gnus/5.130011 (Ma Gnus v0.11) Emacs/24.3 (gnu/linux)

Alex Kost <address@hidden> skribis:

> Ludovic Courtès (2014-08-29 00:09 +0400) wrote:


> OK, I made "" and modified "" and "" (I
> pushed 2 new commits to “emacs-ui” branch).  Is there anything else to
> be done in a build part?

No, that looks good to me.


>>> I think it's a good idea, but if that "name" is just a package name,
>>> I can't use this optimization: I need to define entries by
>>> "name+version".
>> Yes, makes sense.  So that ‘name->entries’ field would map a package
>> name to a list of entries; in the most common case, there’ll be just one
>> entry anyway.  How does that sound?


> Also I'm still not sure about the name ‘manifest-name->entries’ (or
> ‘manifest-name->entry’), as this function returns a vhash, it does not
> transform a name into a list of entries.  It may be confusing, no?

That would be only for internal use anyway, but if you prefer
‘manifest-table’ would do as well.


>>>> Given that ‘set-packages!’ has only on call site, what about removing
>>>> it, and instead writing directly:
>>>>   (define %packages
>>>>     (fold-packages ... vlist-null))
>>>>   (define %package-count
>>>>     (length %packages))
>>>>   (define %package-table
>>>>     (vlist-fold ...))
>>>> It’s also best to prefix global variable names with ‘%’.
> I recalled why I used that ugly ‘set-packages!’: I just didn't want to
> count packages again (i.e. to use ‘length’) for hash-table, so I
> combined setting ‘packages’ variable with counting.

OK, but even when there’s 1M packages, ‘length’ is still going to be
almost instantaneous, so no worries IMO.  ;-)

>> I would make %package-table a vhash instead of a hash table:
>>   (define %package-table
>>     (vlist-fold (lambda (elem result)
>>                   (match elem
>>                     ((name . package)
>>                      (vhash-cons (cons (package-name package)
>>                                        (package-version package))
>>                                  package
>>                                  (if (vhash-assq name result)
>>                                      ...)))))
>>                 vlist-null
>>                 %packages))
> ... I left hash table, because I still don't understand how to use vhash
> for that: a name+version key should give a list of all matching
> packages, but AFAIU your variant would just replace one package with
> another (with the same name+version).

The key is ‘vhash-fold*’ (info "(guile) VHashes").  It allows you to
traverse all the entries associated with a given key:

--8<---------------cut here---------------start------------->8---
scheme@(guile-user)> (vhash-cons '("guile" "2.0") 'foo
                                 (vhash-cons '("guile" "2.0") 'bar
$12 = #<vhash 39240a0 2 pairs>
scheme@(guile-user)> (vhash-fold* cons '() '("guile" "2.0") $12)
$13 = (bar foo)
--8<---------------cut here---------------end--------------->8---

I think that answers your question, right?

> As for ‘set-current-manifest-maybe!’, I'm afraid it can't be deleted.  I
> found that I put it in some places where it shouldn't appear and I fixed
> that, but it still stays in functions returning “package information”
> for the elisp side (for info/list buffers).  Currently I can't invent a
> way how to get rid of this function completely.

I think the profile’s file name could be kept on the elisp side, and
passed to the Scheme code, which wouldn’t need to keep it in a global
variable.  That would also allow guix.el to be used on profiles other
than the default one.

That said, we can look into it later if you prefer.  WDYT?



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