01/20: build: Add cran-uri procedure.

[Ricardo Wurmus]

rekado pushed a commit to branch master
in repository guix.

commit 5546114e73339f61d777eeb4dc3f7ddacaf187e3
Author: Ricardo Wurmus <address@hidden>
Date:   Thu Sep 17 17:00:18 2015 +0200

    build: Add cran-uri procedure.
    
    * guix/build-system/r.scm (cran-uri): New procedure.
---
 guix/build-system/r.scm |   12 +++++++++++-
 1 files changed, 11 insertions(+), 1 deletions(-)

diff --git a/guix/build-system/r.scm b/guix/build-system/r.scm
index 4daec5e..da06cb1 100644
--- a/guix/build-system/r.scm
+++ b/guix/build-system/r.scm
@@ -28,7 +28,8 @@
   #:use-module (srfi srfi-26)
   #:export (%r-build-system-modules
             r-build
-            r-build-system))
+            r-build-system
+            cran-uri))
 
 ;; Commentary:
 ;;
@@ -36,6 +37,15 @@
 ;;
 ;; Code:
 
+(define (cran-uri name version)
+  "Return a list of URI strings for the R package archive on CRAN for the
+release corresponding to NAME and VERSION.  As only the most recent version is
+available via the first URI, the second URI points to the archived version."
+  (list (string-append "mirror://cran/src/contrib/"
+                       name "_" version ".tar.gz")
+        (string-append "mirror://cran/src/contrib/Archive/"
+                       name "/" name "_" version ".tar.gz")))
+
 (define %r-build-system-modules
   ;; Build-side modules imported by default.
   `((guix build r-build-system)