* guix/gexp.scm (<gexp>)[natives]: New field.
(write-gexp): Use both 'gexp-references' and
'gexp-native-references'.
(gexp->derivation): Use both 'gexp-inputs' and 'gexp-native-inputs',
and append them.
(gexp-inputs): Add 'references' parameter and honor it.
(gexp-native-inputs): New procedure.
(gexp->sexp)[reference->sexp]: Add 'native?' parameter and honor it.
Use it, and use 'gexp-native-references'.
(gexp)[collect-native-escapes]: New procedure.
[escape->ref]: Handle 'ungexp-native' and 'ungexp-native-splicing'.
[substitute-ungexp, substitute-ungexp-splicing]: New procedures.
[substitute-references]: Use them, and handle 'ungexp-native' and
'ungexp-native-splicing'.
Adjust generated 'make-gexp' call to provide both normal references
and native references.
[read-ungexp]: Support 'ungexp-native' and
'ungexp-native-splicing'.
Add reader extension for #+.
* tests/gexp.scm (gexp-native-inputs): New procedure.
(gexp->sexp*): Add 'target' parameter.
("ungexp + ungexp-native",
"input list + ungexp-native",
"input list splicing + ungexp-native-splicing",
"gexp->derivation, ungexp-native",
"gexp->derivation, ungexp + ungexp-native"): New tests.
("sugar"): Add tests for #+ and #+@.
* doc/guix.texi (G-Expressions): Document 'ungexp-native' et al.
* guix/gexp.scm (lower-inputs): Add #:system and #:target. Use
'package->cross-derivation' when TARGET is true. Honor SYSTEM.
(gexp->derivation): Add #:target argument. Pass SYSTEM and TARGET to
'lower-inputs' and 'gexp->sexp'.
(gexp->sexp): Add #:system and #:target. Pass them in recursive call
and to 'package-file'.
* tests/gexp.scm (gexp->sexp*): Add 'system' and 'target' parameters.
("gexp->derivation, cross-compilation"): New test.
Partly fixes <http://bugs.gnu.org/18002>.
Reported by David Thompson <dthompson2@worcester.edu>.
* guix/gexp.scm (gexp->derivation): Change #:system to default #f.
Use (%current-system) from within the 'mlet*'.
* tests/gexp.scm ("gexp->derivation, default system"): New test.
* tests/gexp.scm (shebang): New variable.
Skip "gexp->script" when SHEBANG is longer than 127 chars.
* guix/gexp.scm (gexp->script): Add comment on the issue.
* guix/gexp.scm: New file.
* tests/gexp.scm: New file.
* Makefile.am (MODULES): Add guix/gexp.scm.
(SCM_TESTS): Add tests/gexp.scm.
* doc/guix.texi (Derivations): Add #:inputs in 'derivation' example.
Mark 'build-expression->derivation' as deprecated, refer to
"G-Expressions". Remove paragraph about code strata.
(G-Expressions): New node.
