Add Inferior REPL for Emacs

Author: nos1dot618

editor-plugins/emacs/README.md

@@ -1,11 +1,33 @@
-## Thumbnail
+## Lambda Discipline Major Mode for Emacs
 
 ![Thumbnail](./resources/thumbnail.png)
 
-## Getting Started
-
-Right now the only way to use this is to:
+### Getting Started
 
 1. `C-x C-f lbd-mode.el RET`
 2. `M-x eval-buffer RET`
-3. `M-x lbd-mode RET`
+3. `M-x lbd-mode RET`
+
+## Running the REPL inside Emacs
+
+![Thumbnail](./resources/repl_thumbnail.png)
+
+To interact with the `lambda-discipline` REPL directly inside Emacs, you can use the provided `lbd-inf-repl.el` script. This sets up an **inferior REPL buffer** powered by `comint-mode`.
+
+### Getting Started
+
+1. `C-x C-f lbd-inf-repl.el RET`
+2. `M-x eval-buffer RET`
+3. `M-x lbd-run-inf-repl RET`
+
+This will open a buffer called `*lbd*` and start the REPL using `./cmake-build-debug/lbd.exe --repl` with the project root (`../../`) as the working directory.
+
+### Sending Code to the REPL
+
+- Select a region in your buffer and press `C-c C-e` to send it to the REPL.
+- You can also type directly into the `*lbd*` buffer just like a normal shell.
+
+### Notes
+
+- The REPL runs with the project root set as the working directory, so relative paths (e.g. `:load examples/foo.lbd`) work the same as on the command line.
+- If you update the REPL binary, just restart Emacs or rerun `M-x run-lbd`.

editor-plugins/emacs/lbd-inf-repl.el

@@ -0,0 +1,27 @@
+(require 'comint)
+
+(defvar lbd-repl-buffer "*lbd*"
+  "Buffer name for the lambda-discipline REPL.")
+
+(defvar lbd-root-dir
+  (expand-file-name "../../"
+                    (file-name-directory (or load-file-name buffer-file-name)))
+  "Root directory of the lambda-discipline project.")
+
+(defun lbd-run-inf-repl ()
+  "Run an inferior lambda-discipline REPL inside Emacs, rooted at `lbd-root-dir`."
+  (interactive)
+  (let* ((default-directory lbd-root-dir) ; set working dir
+         (exe (expand-file-name "./cmake-build-debug/lbd.exe" lbd-root-dir)))
+    (unless (comint-check-proc lbd-repl-buffer)
+      (set-buffer
+       (apply #'make-comint "lbd" exe nil '("--repl"))))
+    (pop-to-buffer lbd-repl-buffer)))
+
+(defun lbd-send-region (start end)
+  "Send the current region to the lbd process."
+  (interactive "r")
+  (comint-send-region (get-buffer-process lbd-repl-buffer) start end)
+  (comint-send-string (get-buffer-process lbd-repl-buffer) "\n"))
+
+(define-key global-map (kbd "C-c C-e") #'lbd-send-region)