03/04: store: Add 'store-lower'.

[Ludovic Courtès]

civodul pushed a commit to branch master
in repository guix.

commit 023d9892c0411adb523e6bc8337be3e7e94e606f
Author: Ludovic Courtès <address@hidden>
Date:   Wed Jan 14 14:25:58 2015 +0100

    store: Add 'store-lower'.
    
    * guix/store.scm (store-lower): New procedure.
    * tests/store.scm ("store-lower"): New test.
---
 guix/store.scm  |    7 +++++++
 tests/store.scm |    8 +++++++-
 2 files changed, 14 insertions(+), 1 deletions(-)

diff --git a/guix/store.scm b/guix/store.scm
index d3e9462..82ed94b 100644
--- a/guix/store.scm
+++ b/guix/store.scm
@@ -99,6 +99,7 @@
             store-bind
             store-return
             store-lift
+            store-lower
             run-with-store
             %guile-for-build
             text-file
@@ -881,6 +882,12 @@ in the store monad."
                         (procedure-property proc 'documentation))
   result)
 
+(define (store-lower proc)
+  "Lower PROC, a monadic procedure in %STORE-MONAD, to a \"normal\" procedure
+taking the store as its first argument."
+  (lambda (store . args)
+    (run-with-store store (apply proc args))))
+
 ;;
 ;; Store monad operators.
 ;;
diff --git a/tests/store.scm b/tests/store.scm
index cb5370d..f43fcb1 100644
--- a/tests/store.scm
+++ b/tests/store.scm
@@ -1,5 +1,5 @@
 ;;; GNU Guix --- Functional package management for GNU
-;;; Copyright © 2012, 2013, 2014 Ludovic Courtès <address@hidden>
+;;; Copyright © 2012, 2013, 2014, 2015 Ludovic Courtès <address@hidden>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -595,6 +595,12 @@ Deriver: ~a~%"
            (null? (valid-derivers %store file))
            (null? (referrers %store file))))))
 
+(test-equal "store-lower"
+  "Lowered."
+  (let* ((add  (store-lower text-file))
+         (file (add %store "foo" "Lowered.")))
+    (call-with-input-file file get-string-all)))
+
 (test-end "store")