;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2018 Clément Lassieur <clement@lassieur.org>
;;;
;;; This file is part of GNU Guix.
;;;
;;; GNU Guix is free software; you can redistribute it and/or modify it
;;; under the terms of the GNU General Public License as published by
;;; the Free Software Foundation; either version 3 of the License, or (at
;;; your option) any later version.
;;;
;;; GNU Guix is distributed in the hope that it will be useful, but
;;; WITHOUT ANY WARRANTY; without even the implied warranty of
;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
;;; GNU General Public License for more details.
;;;
;;; You should have received a copy of the GNU General Public License
;;; along with GNU Guix.  If not, see <http://www.gnu.org/licenses/>.

(define-module (gnu services utils)
  #:export (push-tokens
            with-tokens-to-list))

(define %tokens-stack (make-parameter #f))

(define (push-tokens . tokens)
  "Push TOKENS to %TOKENS-STACK so that they will be returned by
WITH-TOKENS-TO-LIST."
  (unless (%tokens-stack)
    (error "not called within the dynamic extent of 'with-tokens-to-list'"))
  (%tokens-stack (append (%tokens-stack) tokens)))

(define (with-tokens-to-list thunk)
  "Call THUNK and return the tokens that were pushed to %TOKENS-STACK as a
list."
  (parameterize ((%tokens-stack '()))
    (thunk)
    (%tokens-stack)))

;;; Local Variables:
;;; eval: (put 'with-tokens-to-list 'scheme-indent-function 0)
;;; End: