mw-parser/src/mw_parser/utils.clj

61 lines
2 KiB
Clojure

(ns ^{:doc "Utilities used in more than one namespace within the parser."
:author "Simon Brooke"}
mw-parser.utils)
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;
;; This program 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 2
;; of the License, or (at your option) any later version.
;;
;; This program 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 this program; if not, write to the Free Software
;; Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
;; USA.
;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
(defn rule?
"Return true if the argument appears to be a parsed rule tree, else false."
[maybe-rule]
(and (coll? maybe-rule) (= (first maybe-rule) :RULE)))
(defn TODO
"Marker to indicate I'm not yet finished!"
[message]
message)
(defn suitable-fragment?
"Return `true` if `tree-fragment` appears to be a tree fragment of the expected `type`."
[tree-fragment type]
(and (coll? tree-fragment)
(= (first tree-fragment) type)))
(defn assert-type
"If `tree-fragment` is not a tree fragment of the expected `type`, throw an exception."
[tree-fragment type]
(assert (suitable-fragment? tree-fragment type)
(throw (Exception. (format "Expected a %s fragment" type)))))
(defn search-tree
"Return the first element of this tree which has this tag in a depth-first, left-to-right search"
[tree tag]
(cond
(= (first tree) tag) tree
:else (first
(remove nil?
(map
#(search-tree % tag)
(rest tree))))))