dotemacs · April 20, 2026 13:23 · Apr 20, 2026 · Apr 20, 2026
diff --git a/rdfox-datalog-mode.el b/rdfox-datalog-mode.el
@@ -93,6 +93,22 @@
     st)
   "Syntax table for `rdfox-datalog-mode'.")
 
+(defun rdfox-datalog-syntax-propertize (start end)
+  "Prevent comment syntax from applying to # inside IRI refs between START and END."
+  (save-excursion
+    (goto-char start)
+    (remove-text-properties start end '(syntax-table nil))
+    (while (re-search-forward "<[^>\n]*>" end t)
+      (let ((iri-start (match-beginning 0))
+            (iri-end (match-end 0)))
+        (save-excursion
+          (goto-char iri-start)
+          (while (search-forward "#" iri-end t)
+            (put-text-property (1- (point))
+                               (point)
+                               'syntax-table
+                               (string-to-syntax "."))))))))
+
 (defun rdfox-datalog--previous-significant-line ()
   "Move point to previous non-empty, non-comment line.
 Return point if found, otherwise nil."
@@ -153,6 +169,7 @@ Return point if found, otherwise nil."
   "Major mode for editing RDFox Datalog files."
   :syntax-table rdfox-datalog-mode-syntax-table
   (setq-local font-lock-defaults '(rdfox-datalog-font-lock-keywords))
+  (setq-local syntax-propertize-function #'rdfox-datalog-syntax-propertize)
   (setq-local comment-start "#")
   (setq-local comment-end "")
   (setq-local indent-line-function #'rdfox-datalog-indent-line)

diff --git a/rdfox-datalog-mode.el b/rdfox-datalog-mode.el
@@ -0,0 +1,166 @@
+;;; rdfox-datalog-mode.el --- Major mode for editing RDFox Datalog files -*- lexical-binding: t; -*-
+
+;; Author: Aleksandar Simic <a@repl.ist>
+;; Keywords: languages, convenience
+;; Version: 0.1.0
+
+;; This file is NOT part of GNU Emacs.
+
+;;; Commentary:
+;;
+;; A major mode for editing .dlog files.
+;;
+;; Features:
+;; - Syntax highlighting for RDFox Datalog keywords, built-ins, variables,
+;;   IRIs, literals, and operators.
+;; - # comments.
+;; - Basic indentation.
+;; - Automatic activation for .dlog files.
+
+;;; Code:
+
+(require 'rx)
+
+(defgroup rdfox-datalog nil
+  "Major mode for RDFox Datalog files."
+  :group 'languages)
+
+(defcustom rdfox-datalog-indent-offset 2
+  "Indentation width for `rdfox-datalog-mode'."
+  :type 'integer
+  :group 'rdfox-datalog)
+
+(defconst rdfox-datalog--keywords
+  '("PREFIX" "NOT" "EXIST" "EXISTS" "IN" "FILTER" "BIND" "AS" "AGGREGATE" "ON"
+    "COUNT" "MIN" "MAX" "SUM" "AVG" "DISTINCT")
+  "Datalog keywords understood by the parser package.")
+
+(defconst rdfox-datalog--builtins
+  '("CONCAT" "STR" "IF" "IRI" "SKOLEM" "ROUND" "REGEX")
+  "Built-in RDFox Datalog function names.")
+
+(defconst rdfox-datalog-font-lock-keywords
+  `((,(rx symbol-start (regexp (regexp-opt rdfox-datalog--keywords t)) symbol-end)
+     . font-lock-keyword-face)
+    (,(rx symbol-start (regexp (regexp-opt rdfox-datalog--builtins t)) symbol-end)
+     . font-lock-builtin-face)
+    (,(rx symbol-start (or "true" "false") symbol-end)
+     . font-lock-constant-face)
+    (,(rx "?" (one-or-more (or word ?_)))
+     . font-lock-variable-name-face)
+    (,(rx "_:" (one-or-more (or word ?_)))
+     . font-lock-constant-face)
+    (,(rx "<" (zero-or-more (not (any "\n" ">"))) ">")
+     . font-lock-constant-face)
+    (,(rx symbol-start
+          (one-or-more (or word ?_))
+          ":"
+          (one-or-more (or word ?_))
+          symbol-end)
+     . font-lock-constant-face)
+    (,(rx symbol-start
+          (or ":"
+              (seq (one-or-more (or word ?_)) ":"))
+          symbol-end)
+     . font-lock-constant-face)
+    (,(rx ":" (one-or-more (or word ?_)))
+     . font-lock-constant-face)
+    (,(rx (or ":-" "!=" "<=" ">=" "&&" "||"))
+     . font-lock-keyword-face)
+    (,(rx symbol-start
+          (optional (any "+" "-"))
+          (one-or-more digit)
+          (optional "." (zero-or-more digit))
+          (optional (any "e" "E") (optional (any "+" "-")) (one-or-more digit))
+          symbol-end)
+     . font-lock-constant-face))
+  "Font lock rules for `rdfox-datalog-mode'.")
+
+(defvar rdfox-datalog-mode-syntax-table
+  (let ((st (make-syntax-table)))
+    ;; # comments
+    (modify-syntax-entry ?# "<" st)
+    (modify-syntax-entry ?\n ">" st)
+
+    ;; Strings
+    (modify-syntax-entry ?\" "\"" st)
+    (modify-syntax-entry ?' "\"" st)
+
+    ;; Word constituents for common Datalog tokens.
+    (modify-syntax-entry ?? "_" st)
+    (modify-syntax-entry ?_ "w" st)
+    (modify-syntax-entry ?: "_" st)
+    st)
+  "Syntax table for `rdfox-datalog-mode'.")
+
+(defun rdfox-datalog--previous-significant-line ()
+  "Move point to previous non-empty, non-comment line.
+Return point if found, otherwise nil."
+  (catch 'found
+    (while (zerop (forward-line -1))
+      (back-to-indentation)
+      (unless (or (eolp) (looking-at-p "#"))
+        (throw 'found (point))))
+    nil))
+
+(defun rdfox-datalog--line-starts-with-closing-delimiter-p ()
+  "Return non-nil if current line starts with a closing delimiter or terminal dot."
+  (save-excursion
+    (back-to-indentation)
+    (looking-at-p (rx (or ")" "]" ".")))))
+
+(defun rdfox-datalog--previous-line-opens-body-p ()
+  "Return non-nil if the previous significant line opens a continuation block."
+  (save-excursion
+    (when (rdfox-datalog--previous-significant-line)
+      (end-of-line)
+      (skip-chars-backward " \t")
+      (or (looking-back ":-" (line-beginning-position))
+          (looking-back "[][(),]$" (line-beginning-position))
+          (looking-back ",$" (line-beginning-position))))))
+
+(defun rdfox-datalog-compute-indentation ()
+  "Compute indentation for the current line."
+  (save-excursion
+    (back-to-indentation)
+    (cond
+     ((bobp) 0)
+     ((rdfox-datalog--line-starts-with-closing-delimiter-p)
+      (when (ignore-errors (backward-up-list) t)
+        (current-indentation)))
+     ((rdfox-datalog--previous-line-opens-body-p)
+      (+ (save-excursion
+           (rdfox-datalog--previous-significant-line)
+           (current-indentation))
+         rdfox-datalog-indent-offset))
+     (t
+      (or (save-excursion
+            (when (rdfox-datalog--previous-significant-line)
+              (current-indentation)))
+          0)))))
+
+(defun rdfox-datalog-indent-line ()
+  "Indent current line for `rdfox-datalog-mode'."
+  (interactive)
+  (let ((indent (rdfox-datalog-compute-indentation))
+        (offset (- (current-column) (current-indentation))))
+    (indent-line-to (max indent 0))
+    (when (> offset 0)
+      (move-to-column (+ indent offset)))))
+
+;;;###autoload
+(define-derived-mode rdfox-datalog-mode prog-mode "RDFox-Datalog"
+  "Major mode for editing RDFox Datalog files."
+  :syntax-table rdfox-datalog-mode-syntax-table
+  (setq-local font-lock-defaults '(rdfox-datalog-font-lock-keywords))
+  (setq-local comment-start "#")
+  (setq-local comment-end "")
+  (setq-local indent-line-function #'rdfox-datalog-indent-line)
+  (setq-local indent-tabs-mode nil))
+
+;;;###autoload
+(add-to-list 'auto-mode-alist '("\\.dlog\\'" . rdfox-datalog-mode))
+
+(provide 'rdfox-datalog-mode)
+
+;;; rdfox-datalog-mode.el ends here
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