01/07: doc: Update gexp wrt. extensibility.

[Ludovic Courtès]

civodul pushed a commit to branch wip-build-systems-gexp
in repository guix.

commit 14dfcead773b8ca813af780ba8bb053e720c7ab5
Author: Ludovic Courtès <address@hidden>
Date:   Sat Mar 28 21:16:36 2015 +0100

    doc: Update gexp wrt. extensibility.
    
    This is a followup to bcb1328.
    
    * doc/guix.texi (G-Expressions): Move paragraph about extensibility
      below.  Remove assumptions that things are either packages or
      derivations.
---
 doc/guix.texi |   31 ++++++++++++++++---------------
 1 files changed, 16 insertions(+), 15 deletions(-)

diff --git a/doc/guix.texi b/doc/guix.texi
index 1736503..162d3e8 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -2489,13 +2489,9 @@ Gexps are meant to be written to a file and run or 
manipulated by other
 processes.
 
 @item
-When a package or derivation is unquoted inside a gexp, the result is as
-if its output file name had been introduced.
-
-Actually this mechanism is not limited to package and derivation
-objects; @dfn{compilers} able to ``lower'' other high-level objects to
-derivations can be defined, such that these objects can also be inserted
-into gexps.
+When a high-level object such as a package or derivation is unquoted
+inside a gexp, the result is as if its output file name had been
+introduced.
 
 @item
 Gexps carry information about the packages or derivations they refer to,
@@ -2503,6 +2499,11 @@ and these dependencies are automatically added as inputs 
to the build
 processes that use them.
 @end itemize
 
+Actually this mechanism is not limited to package and derivation
+objects; @dfn{compilers} able to ``lower'' other high-level objects to
+derivations can be defined, such that these objects can also be inserted
+into gexps.
+
 To illustrate the idea, here is an example of a gexp:
 
 @example
@@ -2562,24 +2563,24 @@ or more of the following forms:
 @table @code
 @item address@hidden
 @itemx (ungexp @var{obj})
-Introduce a reference to @var{obj}.  @var{obj} may be a package or a
+Introduce a reference to @var{obj}.  @var{obj} may have one of the
+supported types, for example a package or a
 derivation, in which case the @code{ungexp} form is replaced by its
 output file name---e.g., @code{"/gnu/store/@dots{}-coreutils-8.22}.
 
-If @var{obj} is a list, it is traversed and any package or derivation
-references are substituted similarly.
+If @var{obj} is a list, it is traversed and references to supported
+objects are substituted similarly.
 
 If @var{obj} is another gexp, its contents are inserted and its
 dependencies are added to those of the containing gexp.
 
 If @var{obj} is another kind of object, it is inserted as is.
 
address@hidden address@hidden:@var{output}
address@hidden (ungexp @var{package-or-derivation} @var{output})
address@hidden address@hidden:@var{output}
address@hidden (ungexp @var{obj} @var{output})
 This is like the form above, but referring explicitly to the
address@hidden of @var{package-or-derivation}---this is useful when
address@hidden produces multiple outputs (@pxref{Packages
-with Multiple Outputs}).
address@hidden of @var{obj}---this is useful when @var{obj} produces
+multiple outputs (@pxref{Packages with Multiple Outputs}).
 
 @item address@hidden
 @itemx address@hidden:output