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authorLudovic Courtès <ludo@gnu.org>2016-07-22 14:39:29 +0200
committerLudovic Courtès <ludo@gnu.org>2016-07-22 14:40:54 +0200
commit654c0d97c9de4bf25b9facda1278835883555ae0 (patch)
tree3d399f99fbaa3b54d318b46231cef2a5937a19e4 /doc
parent782170c4f56a43c8bcdd9cffe0bb489e918211a6 (diff)
downloadguix-654c0d97c9de4bf25b9facda1278835883555ae0.tar
guix-654c0d97c9de4bf25b9facda1278835883555ae0.tar.gz
doc: Mention quoting and keywords.
Suggested by Vincent Legoll <vincent.legoll@gmail.com>. * doc/guix.texi (Defining Packages): Remove quasiquote in 'arguments' example. Mention quoting and keywords, with references to Guile's manual.
Diffstat (limited to 'doc')
-rw-r--r--doc/guix.texi34
1 files changed, 33 insertions, 1 deletions
diff --git a/doc/guix.texi b/doc/guix.texi
index e7b233d828..393efab6e4 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -2387,7 +2387,7 @@ package looks like this:
(base32
"0ssi1wpaf7plaswqqjwigppsg5fyh99vdlb9kzl7c9lng89ndq1i"))))
(build-system gnu-build-system)
- (arguments `(#:configure-flags '("--enable-silent-rules")))
+ (arguments '(#:configure-flags '("--enable-silent-rules")))
(inputs `(("gawk" ,gawk)))
(synopsis "Hello, GNU world: An example GNU package")
(description "Guess what GNU Hello prints!")
@@ -2452,12 +2452,44 @@ The @code{arguments} field specifies options for the build system
@var{gnu-build-system} as a request run @file{configure} with the
@code{--enable-silent-rules} flag.
+@cindex quote
+@cindex quoting
+@findex '
+@findex quote
+What about these quote (@code{'}) characters? They are Scheme syntax to
+introduce a literal list; @code{'} is synonymous with @code{quote}.
+@xref{Expression Syntax, quoting,, guile, GNU Guile Reference Manual},
+for details. Here the value of the @code{arguments} field is a list of
+arguments passed to the build system down the road, as with @code{apply}
+(@pxref{Fly Evaluation, @code{apply},, guile, GNU Guile Reference
+Manual}).
+
+The hash-colon (@code{#:}) sequence defines a Scheme @dfn{keyword}
+(@pxref{Keywords,,, guile, GNU Guile Reference Manual}), and
+@code{#:configure-flags} is a keyword used to pass a keyword argument
+to the build system (@pxref{Coding With Keywords,,, guile, GNU Guile
+Reference Manual}).
+
@item
The @code{inputs} field specifies inputs to the build process---i.e.,
build-time or run-time dependencies of the package. Here, we define an
input called @code{"gawk"} whose value is that of the @var{gawk}
variable; @var{gawk} is itself bound to a @code{<package>} object.
+@cindex backquote (quasiquote)
+@findex `
+@findex quasiquote
+@cindex comma (unquote)
+@findex ,
+@findex unquote
+@findex ,@@
+@findex unquote-splicing
+Again, @code{`} (a backquote, synonymous with @code{quasiquote}) allows
+us to introduce a literal list in the @code{inputs} field, while
+@code{,} (a comma, synonymous with @code{unquote}) allows us to insert a
+value in that list (@pxref{Expression Syntax, unquote,, guile, GNU Guile
+Reference Manual}).
+
Note that GCC, Coreutils, Bash, and other essential tools do not need to
be specified as inputs here. Instead, @var{gnu-build-system} takes care
of ensuring that they are present (@pxref{Build Systems}).