+(define %distro-root-directory
+ ;; Absolute file name of the module hierarchy.
+ (dirname (search-path %load-path "guix.scm")))
+
+(define %service-type-path
+ ;; Search path for service types.
+ (make-parameter `((,%distro-root-directory . "gnu/services")
+ (,%distro-root-directory . "gnu/system"))))
+
+(define (all-service-modules)
+ "Return the default set of service modules."
+ (cons (resolve-interface '(gnu services))
+ (all-modules (%service-type-path))))
+
+(define* (fold-service-types proc seed
+ #:optional
+ (modules (all-service-modules)))
+ "For each service type exported by one of MODULES, call (PROC RESULT). SEED
+is used as the initial value of RESULT."
+ (fold-module-public-variables (lambda (object result)
+ (if (service-type? object)
+ (proc object result)
+ result))
+ seed
+ modules))
+