flan/emacs/flan-mode.el
Joseph Ferano 56395edd59 The Emacs client, and the loop is closed
C-c C-c recompiles the top-level form at point and installs it in a running
program at that program's next frame boundary. Verified against sand: an
unsaved buffer edit to game-draw, and 240 consecutive frames drew it.

flan-mode.el derives from prog-mode with lisp-mode's syntax table, which is
most of the work - Flan is s-expressions, so sexp motion, paren matching,
beginning-of-defun and indentation are already right. What it adds is Flan's
own brackets ([ and { are brackets and not symbol characters, since every
binding list and every type is written with them), the characters a name may
contain, and its keywords.

flan-dev.el has no parser in it, which is what the protocol choice bought:
prin1 writes a request, read reads a reply. C-c C-k sends a buffer as one
module rather than a form at a time, because a defvar and the function using it
have to arrive in the same load or the first refers to storage that does not
exist yet. An error comes back with a location and point moves there.

Framing is in bytes and Emacs counts characters, so every length goes through
string-bytes and the process is binary. Otherwise one non-ASCII character in a
buffer puts the reply stream out of step by exactly as many bytes as the
payload has of them - a bug that reads as a corrupt protocol and only appears
for some people. test_emacs.ml drives the real client against a real daemon for
that reason: it is not the same claim as the daemon answering correctly, and a
mistake in the framing, in beginning-of-defun over Flan's syntax table, or in
the reply reader passes test_dev.ml and fails here.
2026-09-10 22:16:44 +07:00

113 lines
4.4 KiB
EmacsLisp

;;; flan-mode.el --- Major mode for Flan -*- lexical-binding: t; -*-
;; Derived from lisp-mode, which is most of the work: Flan is s-expressions, so
;; sexp motion, paren matching, `beginning-of-defun' and indentation all
;; already do the right thing. What is left is what the language actually adds
;; — its own literals and its own set of forms that indent like a body.
;;; Code:
(require 'lisp-mode)
;; The keymap binds them; loading the client is what defines them, and a user
;; may well edit Flan without ever connecting to a running program.
(declare-function flan-eval-defun "flan-dev")
(declare-function flan-eval-buffer "flan-dev")
(declare-function flan-connect "flan-dev")
(declare-function flan-disconnect "flan-dev")
(declare-function flan-describe "flan-dev")
(defgroup flan nil
"Editing and evaluating Flan."
:group 'languages
:prefix "flan-")
(defconst flan--definers
'("defn" "defvar" "defconst" "defstruct" "defunion" "defenum" "defalias"
"declare" "import" "package")
"Forms that introduce a top-level name.")
(defconst flan--special
'("let" "if" "do" "while" "until" "dotimes" "loop" "match" "set" "return"
"defer" "some" "none" "try" "zeroed" "uninit" "slice" "at" "len" "addr"
"bytes" "cast" "true" "false" "nil")
"Forms with meaning to the checker.")
(defvar flan-font-lock-keywords
`((,(concat "(" (regexp-opt flan--definers t) "\\_>"
"[ \t]*\\(\\(?:\\sw\\|\\s_\\)+\\)?")
(1 font-lock-keyword-face)
(2 font-lock-function-name-face nil t))
(,(concat "(" (regexp-opt flan--special t) "\\_>") 1 font-lock-keyword-face)
;; A keyword resolves against an enum at the call site, so it reads as a
;; constant rather than as a string.
("\\_<:\\(?:\\sw\\|\\s_\\)+" . font-lock-constant-face)
;; The machine types, which are ordinary symbols but never anything else.
("\\_<\\(?:[iu]\\(?:8\\|16\\|32\\|64\\)\\|f\\(?:32\\|64\\)\\|bool\\|string\\|Unit\\|Never\\|Ptr\\|Option\\)\\_>"
. font-lock-type-face)
("\\_<\\(?:0x[0-9a-fA-F]+\\|-?[0-9]+\\(?:\\.[0-9]+\\)?\\)\\_>"
. font-lock-constant-face))
"Font lock for `flan-mode'.")
(defvar flan-mode-syntax-table
(let ((table (make-syntax-table lisp-mode-syntax-table)))
;; Flan's own punctuation in names: a name may contain - ? > / and .
(modify-syntax-entry ?? "_" table)
(modify-syntax-entry ?! "_" table)
(modify-syntax-entry ?/ "_" table)
(modify-syntax-entry ?. "_" table)
(modify-syntax-entry ?- "_" table)
;; [ ] and { } are brackets, not symbol characters: every binding list and
;; every type is written with them.
(modify-syntax-entry ?\[ "(]" table)
(modify-syntax-entry ?\] ")[" table)
(modify-syntax-entry ?{ "(}" table)
(modify-syntax-entry ?} "){" table)
table)
"Syntax table for `flan-mode'.")
(defvar flan-mode-map
(let ((map (make-sparse-keymap)))
;; Autoloaded from flan-dev.el, so the client loads on first use.
(define-key map (kbd "C-c C-c") #'flan-eval-defun)
(define-key map (kbd "C-c C-k") #'flan-eval-buffer)
(define-key map (kbd "C-c C-z") #'flan-connect)
(define-key map (kbd "C-c C-q") #'flan-disconnect)
(define-key map (kbd "C-c C-d") #'flan-describe)
map)
"Keymap for `flan-mode'.")
;;;###autoload
(define-derived-mode flan-mode prog-mode "Flan"
"Major mode for editing Flan.
\\{flan-mode-map}"
:syntax-table flan-mode-syntax-table
(setq-local comment-start ";")
(setq-local comment-start-skip ";+ *")
(setq-local comment-add 1)
(setq-local font-lock-defaults '(flan-font-lock-keywords))
(setq-local indent-line-function #'lisp-indent-line)
(setq-local lisp-indent-function #'flan-indent-function)
(setq-local outline-regexp ";;;;+[ \t]*"))
(defun flan-indent-function (indent-point state)
"Indent like Lisp, with Flan's body forms as special forms.
INDENT-POINT and STATE are as for `lisp-indent-function'."
(let ((open (elt state 1)))
(or (and open
(save-excursion
(goto-char (1+ open))
(let ((head (and (looking-at "\\(\\sw\\|\\s_\\)+")
(match-string 0))))
(when (member head '("defn" "let" "if" "while" "until"
"dotimes" "match" "do" "loop" "defer"))
(+ (current-column) 1)))))
(lisp-indent-function indent-point state))))
;;;###autoload
(add-to-list 'auto-mode-alist '("\\.flan\\'" . flan-mode))
(provide 'flan-mode)
;;; flan-mode.el ends here