store: Add 'store-lower'.

* guix/store.scm (store-lower): New procedure.
* tests/store.scm ("store-lower"): New test.

1 files changed, 7 insertions, 0 deletions

diff --git a/guix/store.scm b/guix/store.scm
index d3e94625a7..82ed94bbc1 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.
 ;;