1 files changed, 62 insertions, 6 deletions

diff --git a/guix/build-system.scm b/guix/build-system.scm
index c618a5e243..f185d5704f 100644
--- a/guix/build-system.scm
+++ b/guix/build-system.scm
@@ -1,5 +1,5 @@
 ;;; GNU Guix --- Functional package management for GNU
-;;; Copyright © 2012, 2013 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2012, 2013, 2014 Ludovic Courtès <ludo@gnu.org>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -18,17 +18,73 @@
 
 (define-module (guix build-system)
   #:use-module (guix records)
+  #:use-module (ice-9 match)
   #:export (build-system
             build-system?
             build-system-name
             build-system-description
-            build-system-builder
-            build-system-cross-builder))
+            build-system-lower
+
+            bag
+            bag?
+            bag-name
+            bag-build-inputs
+            bag-host-inputs
+            bag-target-inputs
+            bag-outputs
+            bag-arguments
+            bag-build
+
+            make-bag))
 
 (define-record-type* <build-system> build-system make-build-system
   build-system?
   (name        build-system-name)         ; symbol
   (description build-system-description)  ; short description
-  (build       build-system-builder)      ; (store system name source inputs)
-  (cross-build build-system-cross-builder ; (store system x-system ...)
-               (default #f)))
+  (lower       build-system-lower))       ; args ... -> bags
+
+;; "Bags" are low-level representations of "packages".  Here we use
+;; build/host/target in the sense of the GNU tool chain (info "(autoconf)
+;; Specifying Target Triplets").
+(define-record-type* <bag> bag %make-bag
+  bag?
+  (name          bag-name)               ;string
+  (build-inputs  bag-build-inputs        ;list of packages
+                 (default '()))
+  (host-inputs   bag-host-inputs         ;list of packages
+                 (default '()))
+
+  ;; "Target inputs" are packages that are built natively, but that are used
+  ;; by target programs in a cross-compilation environment.  Thus, they act
+  ;; like 'inputs' as far as search paths are concerned.  The only example of
+  ;; that is the cross-libc: it is an input of 'cross-gcc', thus built
+  ;; natively; yet, we want it to be considered as a target input for the
+  ;; purposes of $CPATH, $LIBRARY_PATH, etc.
+  (target-inputs bag-target-inputs
+                 (default '()))
+
+  (outputs       bag-outputs             ;list of strings
+                 (default '("out")))
+  (arguments     bag-arguments           ;list
+                 (default '()))
+  (build         bag-build))             ;bag -> derivation
+
+(define* (make-bag build-system name
+                   #:key source (inputs '()) (native-inputs '())
+                   (outputs '()) (arguments '())
+                   target)
+  "Ask BUILD-SYSTEM to return a 'bag' for NAME, with the given SOURCE,
+INPUTS, NATIVE-INPUTS, OUTPUTS, and additional ARGUMENTS.  If TARGET is not
+#f, it must be a string with the GNU triplet of a cross-compilation target.
+
+This is the mechanism by which a package is \"lowered\" to a bag, which is the
+intermediate representation just above derivations."
+  (match build-system
+    (($ <build-system> _ description lower)
+     (apply lower name
+            #:source source
+            #:inputs inputs
+            #:native-inputs native-inputs
+            #:outputs outputs
+            #:target target
+            arguments))))