From mboxrd@z Thu Jan  1 00:00:00 1970
From: ludo@gnu.org (Ludovic =?utf-8?Q?Court=C3=A8s?=)
Subject: Thunked package =?utf-8?B?4oCYYXJndW1lbnRz4oCZ?=
Date: Wed, 23 Jan 2013 23:35:12 +0100
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Hi!

With commit 21c203a, the =E2=80=98arguments=E2=80=99 field of packages is a=
utomatically
=E2=80=9Cthunked=E2=80=9D=E2=80=93i.e., wrapped in a zero-argument closure.=
  This allows the
value of =E2=80=98arguments=E2=80=99 to refer to the =E2=80=98%current-syst=
em=E2=80=99 fluid to do all
things system-specific.

Previously, when the value of =E2=80=98arguments=E2=80=99 was system-depend=
ent, one had
to write:

  (arguments (lambda (system)
               (if (string=3D? system "i686-linux")
                   ...)))

Now, one can just write:

  (arguments (if (string=3D? (%current-system) "i686-linux")
                 ...))

... and =E2=80=98%current-system=E2=80=99 is called within the dynamic exte=
nt of
=E2=80=98package-derivation=E2=80=99 (IOW, it does the right thing, if you =
prefer. ;-))

Yet, =E2=80=98package-arguments=E2=80=99 always returns a list, transparent=
ly calling
the thunk.

This leads to a more concise style, simplifies code in many places, and
is more extensible (for instance, adding (%cross-system) when
cross-compilation is supported will be trivial.)

You should now run =E2=80=98make clean && make=E2=80=99.

I think I have converted all the places that had a lambda as their
=E2=80=98arguments=E2=80=99, or that tested the return type of =E2=80=98pro=
cedure-arguments=E2=80=99,
but I could have left some.  So please report any issues!

Eventually I=E2=80=99ll change other fields to be thunked, such as =E2=80=
=98inputs=E2=80=99.

Thanks,
Ludo=E2=80=99.