feat: add GNU emacs editor plugin

Author: nos1dot618

README.md

@@ -41,7 +41,13 @@ lbd [options]
 
 ---
 
-### TODO
+## Editor Plugins
+
+1. [GNU Emacs](./editor-plugins/emacs)
+
+---
+
+## TODO
 
 - TODO: Add build instructions for Windows (MSVC toolchain).
 - TODO: Provide better examples (e.g., Advent of Code snippets).

editor-plugins/emacs/README.md

@@ -0,0 +1,11 @@
+## Thumbnail
+
+![Thumbnail](./resources/thumbnail.png)
+
+## Getting Started
+
+Right now the only way to use this is to:
+
+1. `C-x C-f lbd-mode.el RET`
+2. `M-x eval-buffer RET`
+3. `M-x lbd-mode RET`

editor-plugins/emacs/lbd-mode.el

@@ -0,0 +1,131 @@
+;;; lbd-mode.el --- Major mode for Lambda-Discipline Language -*- lexical-binding: t; -*-
+;;
+;; Author: NinthCircle
+;; Version: 0.1
+;; Keywords: languages
+;; URL: https://gitlab.com/ninthcircle/lambda-discipline/-/tree/master/editor-plugins/emacs/lbd-mode.el
+
+(defvar lbd-mode-hook nil)
+
+(defvar lbd-mode-map
+  (let ((map (make-sparse-keymap)))
+    map)
+  "Keymap for lbd major mode")
+
+;; Syntax table
+(defvar lbd-mode-syntax-table
+  (let ((st (make-syntax-table)))
+    ;; Comment syntax: “--” starts a comment, newline ends it
+    (modify-syntax-entry ?- ". 12" st)
+    (modify-syntax-entry ?\n ">" st)
+
+    ;; Parentheses
+    (modify-syntax-entry ?\( "(" st)
+    (modify-syntax-entry ?\) ")" st)
+
+    ;; You can tweak these if you want string/char support later
+    (modify-syntax-entry ?\" "\"" st)
+    (modify-syntax-entry ?' "w" st)
+
+    st)
+  "Syntax table for lbd-mode.")
+
+;; Comment settings
+(setq-local comment-start "-- ")
+(setq-local comment-end "")
+
+;; Font lock
+(defconst lbd--keywords
+  '("true" "false" "if_then" "pair" "first" "second" "use")
+  "Language keywords for lbd-mode.")
+
+(defvar lbd-font-lock-keywords
+  (let* ((kw (regexp-opt lbd--keywords 'words))
+         ;; types are capitalized identifiers like Any Bool Float
+         (type-re "\\b\\([A-Z][A-Za-z0-9_]*\\)\\b")
+         ;; arrows
+         (arrow-re "->")
+         ;; lambda/backslash `\` and the dot that follows the argument list
+         (lambda-re "\\\\[[:alnum:]_]+:\\s-*\\([A-Za-z0-9_<>]+\\)\\.\\|\\\\")
+         ;; top-level defs: name : type =
+         (def-re "^\\s-*\\([a-zA-Z_][a-zA-Z0-9_?']*\\)\\s-*:")
+         )
+    `(
+      (,kw . font-lock-keyword-face)
+      (,type-re 1 font-lock-type-face)
+      (,arrow-re . font-lock-builtin-face)
+      ("\\\\" . font-lock-builtin-face) ;; the backslash lambda
+      ("\\." . font-lock-constant-face) ;; dots as separators
+      ;; highlight top-level names like `name:` at bol
+      (,def-re 1 font-lock-function-name-face)
+      ))
+  "Font lock patterns for lbd-mode.")
+
+;; Indentation
+(defun lbd--calculate-indent ()
+  "Calculate indentation for current line in `lbd-mode'.
+Returns number of spaces to indent to.
+This implementation uses parenthesis depth as a baseline and adds
+4 spaces for continued lines after a dot or after a lambda argument list."
+  (save-excursion
+    (beginning-of-line)
+    (let* ((parse (syntax-ppss))
+           (paren-depth (nth 0 parse))
+           indent)
+      (cond
+       ;; If inside parens, align with the opening paren plus two spaces
+       ((> paren-depth 0)
+        (goto-char (nth 1 parse))
+        (setq indent (+ (current-column) 2)))
+       ;; If previous non-blank line ends with '.' or is a lambda start, indent
+       (t
+        (save-excursion
+          (forward-line -1)
+          (while (and (not (bobp)) (looking-at "^\\s-*$"))
+            (forward-line -1))
+          (end-of-line)
+          (cond
+           ((looking-back "\\\\.*\\.\\s-*" (line-beginning-position))
+            (setq indent (+ (current-indentation) 4)))
+           ((looking-back "\\\\" (line-beginning-position))
+            (setq indent (+ (current-indentation) 4)))
+           ((looking-back "\\.\\s-*" (line-beginning-position))
+            (setq indent (+ (current-indentation) 4)))
+           (t (setq indent 0))))))
+      (max indent 0))))
+
+(defun lbd-indent-line ()
+  "Indent current line as lbd code."
+  (interactive)
+  (let ((indent (lbd--calculate-indent))
+        (offset (- (current-column) (current-indentation))))
+    (if indent
+        (progn
+          (indent-line-to indent)
+          (when (> offset 0) (forward-char offset)))
+      (indent-line-to 0))))
+
+;; Imenu support
+(defvar lbd-imenu-generic-expression
+  '(( "Definitions" "^\\s-*\\([a-zA-Z_][a-zA-Z0-9_?']*\\)\\s-*:" 1))
+  "Imenu expression for lbd-mode to index top-level definitions.")
+
+;;;###autoload
+(define-derived-mode lbd-mode prog-mode "LBD"
+  "Major mode for editing Lambda-Discipline-like files."
+  :syntax-table lbd-mode-syntax-table
+  (setq-local font-lock-defaults '(lbd-font-lock-keywords))
+  ;; comment style
+  (setq-local comment-start "-- ")
+  (setq-local comment-end "")
+  ;; indentation
+  (setq-local indent-line-function #'lbd-indent-line)
+  ;; imenu
+  (setq-local imenu-generic-expression lbd-imenu-generic-expression))
+
+;;;###autoload
+(add-to-list 'auto-mode-alist '("\\.lbd\\'" . lbd-mode))
+(add-to-list 'auto-mode-alist '("\\.lambda\\'" . lbd-mode))
+
+(provide 'lbd-mode)
+;;; lbd-mode.el ends here

editor-plugins/emacs/resources/thumbnail.png

@@ -2,8 +2,8 @@ true: Bool = \x: Any. \y: Any. x
 false: Bool = \x: Any. \y: Any. y
 
 ifthen: Any = \condition: Bool -> Any -> Any -> Any.
-	\then_clause: Any. \else_clause: Any.
-	(condition then_clause else_clause)
+    \then_clause: Any. \else_clause: Any.
+        (condition then_clause else_clause)
 
 (print (ifthen true "True" "False"))
-(print (ifthen false "True" "False"))
+(print (ifthen false "True" "False"))