From 06e4362f601fcdacadc5f158b40b079d34688b21 Mon Sep 17 00:00:00 2001
From: David Thompson <dthompson2@worcester.edu>
Date: Mon, 19 Oct 2015 09:12:50 -0400
Subject: Add XML highlighter.

* syntax-highlight/xml.scm: New file
* Makefile.am (SOURCES): Add it.
* README ("Supported Languages"): Add "XML."
---
 syntax-highlight/xml.scm | 111 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 111 insertions(+)
 create mode 100644 syntax-highlight/xml.scm

(limited to 'syntax-highlight/xml.scm')

diff --git a/syntax-highlight/xml.scm b/syntax-highlight/xml.scm
new file mode 100644
index 0000000..371f36f
--- /dev/null
+++ b/syntax-highlight/xml.scm
@@ -0,0 +1,111 @@
+;;; guile-syntax-highlight --- General-purpose syntax highlighter
+;;; Copyright © 2015 David Thompson <davet@gnu.org>
+;;;
+;;; Guile-syntax-highlight is free software; you can redistribute it
+;;; and/or modify it under the terms of the GNU Lesser General Public
+;;; License as published by the Free Software Foundation; either
+;;; version 3 of the License, or (at your option) any later version.
+;;;
+;;; Guile-syntax-highlight 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 Lesser General Public License for more details.
+;;;
+;;; You should have received a copy of the GNU Lesser General Public
+;;; License along with guile-syntax-highlight.  If not, see
+;;; <http://www.gnu.org/licenses/>.
+
+;;; Commentary:
+;;
+;; Syntax highlighting for Scheme.
+;;
+;;; Code:
+
+(define-module (syntax-highlight xml)
+  #:use-module (ice-9 match)
+  #:use-module (srfi srfi-1)
+  #:use-module (srfi srfi-11)
+  #:use-module (srfi srfi-41)
+  #:use-module (syntax-highlight parsers)
+  #:export (xml-highlighter))
+
+(define (flatten+compact highlights)
+  (define tagged?
+    (match-lambda
+      (((? symbol?) _) #t)
+      (_ #f)))
+
+  (let loop ((highlights highlights)
+             (result '()))
+    (match highlights
+      (() (reverse result))
+      (("" . tail)
+       (loop tail result))
+      (((or (? string? head) (? tagged? head)) . tail)
+       (loop tail (cons head result)))
+      ((head . tail)
+       (loop tail (append (reverse (flatten+compact head)) result))))))
+
+(define parse-comment
+  (tagged-parser 'comment (parse-delimited "<!--" #:until "-->")))
+
+(define parse-xml-symbol
+  (parse-char-set
+   (char-set-union char-set:letter+digit
+                   (char-set #\. #\- #\_ #\:))))
+
+(define parse-element-name
+  (tagged-parser 'element parse-xml-symbol))
+
+(define parse-whitespace-maybe
+  (parse-maybe parse-whitespace))
+
+(define parse-attribute
+  (parse-each (tagged-parser 'attribute parse-xml-symbol)
+              parse-whitespace-maybe
+              (parse-string "=")
+              parse-whitespace-maybe
+              (tagged-parser 'string (parse-delimited "\""))))
+
+(define parse-open-tag
+  (parse-each (tagged-parser 'open (parse-any (parse-string "<?")
+                                              (parse-string "<")))
+              parse-element-name
+              (parse-many
+               (parse-any (parse-each
+                           parse-whitespace
+                           parse-attribute)
+                          parse-whitespace))
+              (tagged-parser 'close (parse-any (parse-string ">")
+                                               (parse-string "/>")
+                                               (parse-string "?>")))))
+
+(define parse-close-tag
+  (parse-each (tagged-parser 'open (parse-string "</"))
+              parse-element-name
+              (tagged-parser 'close (parse-string ">"))))
+
+(define char-set:not-whitespace
+  (char-set-complement char-set:whitespace))
+
+(define parse-tag
+  (parse-each (parse-string "<")
+              (parse-char-set
+               (char-set-delete char-set:not-whitespace #\>))
+              (parse-string ">")))
+
+(define parse-entity
+  (tagged-parser 'entity (parse-delimited "&" #:until ";")))
+
+(define parse-text
+  (parse-char-set
+   (char-set-difference char-set:full (char-set #\<))))
+
+(define xml-highlighter
+  (parse-map flatten+compact
+             (parse-many
+              (parse-any parse-comment
+                         parse-open-tag
+                         parse-close-tag
+                         parse-entity
+                         parse-text))))
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