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Re: [PATCH] gnu-maintenance: Improve 'official-gnu-packages'; add the re

From: Ludovic Courtès
Subject: Re: [PATCH] gnu-maintenance: Improve 'official-gnu-packages'; add the related procedures.
Date: Tue, 26 Mar 2013 21:50:57 +0100
User-agent: Gnus/5.130005 (Ma Gnus v0.5) Emacs/24.2 (gnu/linux)

Nikita Karetnikov <address@hidden> skribis:

>> “Eval is evil”, as lispers love to say.
> Yeah, I've heard this one.
>> It should never be used, unless there’s a very good reason to do so.
> I've heard this too.  But people always fail to explain the "a very good
> reason" part.

There are many reasons, including: it’s hard to reason about code
generated at run time, it’s easy to generate invalid code, generated
code cannot be compiled & optimized, and evaluating code is much slower
than running compiled code.

>> In my unfinished binary substitute where a similar situation arises,
>> I’ve done this:
> [...]
>> And then, it is used like this:
>>          (alist->record properties
>>                         (cut %make-cache url <...>)
>>                         '("StoreDir" "WantMassQuery"))
> So, keys and values are strings here, right?

Keys are strings, and values can be anything.

> But I want to store setters as values.

The suggestion I made was in favor of using a single
‘make-gnu-record-descriptor’ call with all the field values (as opposed
to creating the record with all fields set to #f, and then using
‘setters’ to change them to their actual value.)

In the example above, the end result is a single call to the
constructor, equivalent to:

  (%make-cache url
               (assoc-ref properties "StoreDir")
               (assoc-ref properties "WantMassQuery"))


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