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authorLudovic Courtès <ludo@gnu.org>2015-08-26 11:28:23 +0200
committerLudovic Courtès <ludo@gnu.org>2015-08-27 00:49:23 +0200
commitc2b8467645bb2c2e17eb9c580f39e345c4dc2f4a (patch)
tree754462cfbcccdb8c58f000ee5bf88d064279b657 /doc
parentf7283db37d58f1a7dede5f410c6c0a75aa82b12e (diff)
gexp: Add 'lower-object'.
* guix/gexp.scm (lower-object): New procedure. (lower-inputs, lower-references, gexp->sexp): Use it. * tests/gexp.scm ("lower-object"): New test. * doc/guix.texi (G-Expressions): Document it.
Diffstat (limited to 'doc')
-rw-r--r--doc/guix.texi18
1 files changed, 17 insertions, 1 deletions
diff --git a/doc/guix.texi b/doc/guix.texi
index f05376efcf..39093a9c98 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -3125,9 +3125,11 @@ and these dependencies are automatically added as inputs to the build
processes that use them.
@end itemize
+@cindex lowering, of high-level objects in gexps
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
+derivations or files in the store can be defined,
+such that these objects can also be inserted
into gexps. For example, a useful type of high-level object that can be
inserted in a gexp is ``file-like objects'', which make it easy to
add files to the store and refer to them in
@@ -3400,6 +3402,20 @@ also modules containing build tools. To make it clear that they are
meant to be used in the build stratum, these modules are kept in the
@code{(guix build @dots{})} name space.
+@cindex lowering, of high-level objects in gexps
+Internally, high-level objects are @dfn{lowered}, using their compiler,
+to either derivations or store items. For instance, lowering a package
+yields a derivation, and lowering a @code{plain-file} yields a store
+item. This is achieved using the @code{lower-object} monadic procedure.
+
+@deffn {Monadic Procedure} lower-object @var{obj} [@var{system}] @
+ [#:target #f]
+Return as a value in @var{%store-monad} the derivation or store item
+corresponding to @var{obj} for @var{system}, cross-compiling for
+@var{target} if @var{target} is true. @var{obj} must be an object that
+has an associated gexp compiler, such as a @code{<package>}.
+@end deffn
+
@c *********************************************************************
@node Utilities