services: 'service-parameters' becomes 'service-value'.

* gnu/services.scm (<service>)[parameters]: Rename to...
[value]: ... this.
Change calls to 'service-parameters' to 'service-value'.
* gnu/system.scm, gnu/tests/base.scm,
guix/scripts/system.scm, tests/services.scm: Likewise.
* doc/guix.texi (Service Reference): Adjust accordingly.

doc/guix.texi

@@ -15684,7 +15684,7 @@ Return true if @var{obj} is a service.
 Return the type of @var{service}---i.e., a @code{<service-type>} object.
 @end deffn
 
-@deffn {Scheme Procedure} service-parameters @var{service}
+@deffn {Scheme Procedure} service-value @var{service}
 Return the value associated with @var{service}.  It represents its
 parameters.
 @end deffn

gnu/services.scm

@@ -51,7 +51,8 @@ (define-module (gnu services)
             service
             service?
             service-kind
-            service-parameters
+            service-value
+            service-parameters                    ;deprecated
 
             simple-service
             modify-services
@@ -142,10 +143,14 @@ (define (write-service-type type port)
 
 ;; Services of a given type.
 (define-record-type <service>
-  (service type parameters)
+  (service type value)
   service?
   (type       service-kind)
-  (parameters service-parameters))
+  (value      service-value))
+
+(define service-parameters
+  ;; Deprecated alias.
+  service-value)
 
 (define (simple-service name target value)
   "Return a service that extends TARGET with VALUE.  This works by creating a
@@ -161,7 +166,7 @@ (define-syntax %modify-service
      service)
     ((_ svc (kind param => exp ...) clauses ...)
      (if (eq? (service-kind svc) kind)
-         (let ((param (service-parameters svc)))
+         (let ((param (service-value svc)))
            (service (service-kind svc)
                     (begin exp ...)))
          (%modify-service svc clauses ...)))))
@@ -321,7 +326,7 @@ (define (directory-union name things)
 (define* (activation-service->script service)
   "Return as a monadic value the activation script for SERVICE, a service of
 ACTIVATION-SCRIPT-TYPE."
-  (activation-script (service-parameters service)))
+  (activation-script (service-value service)))
 
 (define (activation-script gexps)
   "Return the system's activation script, which evaluates GEXPS."
@@ -432,7 +437,7 @@ (define (extra-special-file file target)
 
 (define (etc-directory service)
   "Return the directory for SERVICE, a service of type ETC-SERVICE-TYPE."
-  (files->etc-directory (service-parameters service)))
+  (files->etc-directory (service-value service)))
 
 (define (files->etc-directory files)
   (file-union "etc" files))
@@ -605,7 +610,7 @@ (define (apply-extension target)
       (match (find (matching-extension target)
                    (service-type-extensions (service-kind service)))
         (($ <service-extension> _ compute)
-         (compute (service-parameters service))))))
+         (compute (service-value service))))))
 
   (match (filter (lambda (service)
                    (eq? (service-kind service) target-type))
@@ -616,7 +621,7 @@ (define (apply-extension target)
               (extensions (map (apply-extension sink) dependents))
               (extend     (service-type-extend (service-kind sink)))
               (compose    (service-type-compose (service-kind sink)))
-              (params     (service-parameters sink)))
+              (params     (service-value sink)))
          ;; We distinguish COMPOSE and EXTEND because PARAMS typically has a
          ;; different type than the elements of EXTENSIONS.
          (if extend

gnu/system.scm

@@ -615,7 +615,7 @@ (define* (operating-system-boot-script os #:key container?)
   (let* ((services (operating-system-services os #:container? container?))
          (boot     (fold-services services #:target-type boot-service-type)))
     ;; BOOT is the script as a monadic value.
-    (service-parameters boot)))
+    (service-value boot)))
 
 (define (operating-system-user-accounts os)
   "Return the list of user accounts of OS."
@@ -623,12 +623,12 @@ (define (operating-system-user-accounts os)
          (account  (fold-services services
                                   #:target-type account-service-type)))
     (filter user-account?
-            (service-parameters account))))
+            (service-value account))))
 
 (define (operating-system-shepherd-service-names os)
   "Return the list of Shepherd service names for OS."
   (append-map shepherd-service-provision
-              (service-parameters
+              (service-value
                (fold-services (operating-system-services os)
                               #:target-type
                               shepherd-root-service-type))))
@@ -638,7 +638,7 @@ (define* (operating-system-derivation os #:key container?)
   (let* ((services (operating-system-services os #:container? container?))
          (system   (fold-services services)))
     ;; SYSTEM contains the derivation as a monadic value.
-    (service-parameters system)))
+    (service-value system)))
 
 (define* (operating-system-profile os #:key container?)
   "Return a derivation that builds the system profile of OS."

gnu/tests/base.scm

@@ -56,7 +56,7 @@ (define* (run-basic-test os command #:optional (name "basic")
 inserted before the first test.  This is used to introduce an extra
 initialization step, such as entering a LUKS passphrase."
   (define special-files
-    (service-parameters
+    (service-value
      (fold-services (operating-system-services os)
                     #:target-type special-files-service-type)))
 

guix/scripts/system.scm

@@ -289,7 +289,7 @@ (define (upgrade-shepherd-services os)
 running service.  Unloading or stopping the wrong service ('udev', say) could
 bring the system down."
   (define new-services
-    (service-parameters
+    (service-value
      (fold-services (operating-system-services os)
                     #:target-type shepherd-root-service-type)))
 
@@ -487,7 +487,7 @@ (define (reinstall-grub store number)
 (define (service-node-label service)
   "Return a label to represent SERVICE."
   (let ((type  (service-kind service))
-        (value (service-parameters service)))
+        (value (service-value service)))
     (string-append (symbol->string (service-type-name type))
                    (cond ((or (number? value) (symbol? value))
                           (string-append " " (object->string value)))
@@ -711,7 +711,7 @@ (define (export-shepherd-graph os port)
   (let* ((services  (operating-system-services os))
          (pid1      (fold-services services
                                    #:target-type shepherd-root-service-type))
-         (shepherds (service-parameters pid1)) ;list of <shepherd-service>
+         (shepherds (service-value pid1))         ;list of <shepherd-service>
          (sinks     (filter (lambda (service)
                               (null? (shepherd-service-requirement service)))
                             shepherds)))

tests/services.scm

@@ -1,5 +1,5 @@
 ;;; GNU Guix --- Functional package management for GNU
-;;; Copyright © 2015, 2016 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2015, 2016, 2017 Ludovic Courtès <ludo@gnu.org>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -75,7 +75,7 @@ (define live-service
                                         (iota 5 1)))
                             #:target-type t1)))
     (and (eq? (service-kind r) t1)
-         (service-parameters r))))
+         (service-value r))))
 
 (test-assert "fold-services, ambiguity"
   (let* ((t1 (service-type (name 't1) (extensions '())