Lem Manual for Users

The documentation is in progress. You can find a first list of available keys and commands in default-keybindings.md.

NEW! Lem has a web page, in progress too: https://lem-project.github.io/lem-page/usage/keybindings/

Lem Manual for Users

Lem has Emacs-like keybindings, as well as a vi emulation (M-x vi-mode).

So, to open a file, press C-x C-f (you get the file selection dialog shown above). To save it, it's C-x C-s. To save many buffers at once, C-x s.

To switch to the REPL: C-c C-z.

To compile and load a buffer: C-c C-k. To compile a function: C-c C-c.

To switch windows (aka splits of a screen): C-x o ('o' letter) and M-o. To make a window fullscreen: C-x 1. To split it vertically: C-x 3 and horizontally: C-x 2. To make the current window disappear: C-x 0 (zero).

To switch buffers: C-x b.

To run an interactive command: M-x (alt-x).

To evaluate some Lisp code: M-:.

To show the context menu: Shift-F10.

See this Emacs & Slime cheatsheet to find more: https://lispcookbook.github.io/cl-cookbook/emacs-ide.html#appendix

Switching buffers

Use C-x b (aka M-x list-buffers). But don't stop here, it's a rich command.

You are presented a "modale" window. Type some text to start narrowing the buffers list matching your entry.

You can also use Space to select/deselect entries, then use a right click to choose an action to apply on the selected buffers. Default actions are to kill the selected buffers, or to save them.

vi and emacs modes

Use M-x vi-mode and M-x emacs-mode.

Describe keys

To know what function is bound to a key binding, use M-x describe-key (C-x ?).

Describe available bindings

To see the currently available key bindings, use M-x describe-bindings.

See also describe-mode, to understand in which mode the editor is in the current buffer.

grep

M-x grep

this presents the results in a two-panes window. You can edit lines in the results buffer, changes are reflected immediately on the files, and updated on the right side. You can use search and replace M-x query-replace in the results buffer.

multiple cursors

Use M-C (Alt and capital c), `M-x add-cursors-to-next-line) to add a cursor to the next line.

Working with a language's Language Server Protocol (LSP)

For Go, if you have gopls, it should work without doing anything.

Otherwise, configurations are required.

JavaScript

An example JS config for LSP:

(lem-lsp-mode/lsp-mode::define-language-spec 
    (js-spec lem-js-mode:js-mode)
  ;; thanks @sasanidas
  :language-id "javascript"
  :root-uri-patterns '("package.json" "tsconfig.json")
  :command '("typescript-language-server" "--stdio")
  :install-command "npm install -g typescript-language-server typescript"
  :readme-url "https://github.com/typescript-language-server/typescript-language-server"
  :connection-mode :stdio)

Supported languages

To see all supported languages and modes, see the modes/ directory.

Languages include: asm, c, css, dart, go, haskell, html, java, js, lisp, nim, ocaml, python, rust, scala, scheme, shell, sql…

Other modes include: asciidoc, dot, json, lsp, makefile, paredit, patch, posix-shell, review, vi, yaml…

Python

python-mode supports:

• syntax highlighting
• M-x run-python command
• M-x python-eval-region

Elixir

elixir-mode (preliminary work merged on 30th, May 2023) adds:

• syntax highlighting
• preliminary LSP support
• M-x run-elixir command
• M-x elixir-eval-region

For more information: https://github.com/lem-project/lem/pull/647

Go

• syntax highlighting
• M-x go-electric-close, gofmt, godoc, godef-describe, goflymake with inline annotations, M-x go-remove-notes to delete the overlays.

This is the default LSP configuration:

;; in modes/go-mode/lsp-config.lisp
(define-language-spec (go-spec lem-go-mode:go-mode)
  :language-id "go"
  :root-uri-patterns '("go.mod")
  :command (lambda (port) `("gopls" "serve" "-port" ,(princ-to-string port)))
  :install-command "go install golang.org/x/tools/gopls@latest"
  :readme-url "https://github.com/golang/tools/tree/master/gopls"
  :connection-mode :tcp)

Guile

Example config:

;; thks sasanidas
(setf lem-scheme-mode::*default-port* 4010
      lem-scheme-mode::*use-scheme-autodoc* :auto
      lem-scheme-mode::*scheme-swank-server-run-command* 
      '("guile" "--r7rs"
        "-l" "lisp/scheme/r7rs-swank/guile-swank.scm" 
        "-c" "(import (guile-swank)) (start-swank)")
      lem-scheme-mode::*use-scheme-repl-shortcut* t ) 

Rust

• syntax highlighting, go to beginning/end of function, indentation…
• format buffer (see *rust-format-buffer* which defaults to "rustfmt"), format on save hook (see *rust-format-on-save* which defaults to t)
• preliminary support for find definition.

Default keys:

(define-key *rust-mode-keymap* "C-c C-f" 'rust-format-buffer)
(define-key *rust-mode-keymap* "M-C-q" 'indent-exp)

Writing one's own commands

Use define-command:

(in-package :lem)
(define-command open-init-file () ()
    ;; @sasanidas
    (lem:find-file 
        (merge-pathnames "init.lisp" (lem-home))))

or copy-paste this with M-:

(lem:define-command open-init-file () ()
    (lem:find-file 
        (merge-pathnames "init.lisp" (lem:lem-home))))

You can now call it with M-x open-init-file.

Defining a new color theme (Monokai example)

(if none of the 100 available in Lem 2.0 don't satisfy you, see M-x list-color-themes).

;; thanks https://gist.github.com/jason-chandler/6332e3fd753fa87e3b1cd13582df5862
(define-color-theme "monokai" ()
  (:foreground "#eeeeee")
  (:background "#262626")
  (cursor :foreground "#262626" :background "#eeeeee")
  (syntax-warning-attribute :foreground "#87005f" :background "#262626")
  (syntax-string-attribute :foreground "#d7d787" :background "#262626")
  (syntax-comment-attribute :foreground "#666666" :background "#262626")
  (syntax-keyword-attribute :foreground "#5fd7ff" :background "#262626")
  (syntax-constant-attribute :foreground "#5fd7ff" :background "#262626")
  (syntax-function-name-attribute :foreground "#afd700" :background "#262626")
  (syntax-variable-attribute :foreground nil :background "#262626")
  (syntax-type-attribute :foreground nil :background "#262626")
  (syntax-builtin-attribute :foreground nil :background "#262626"))

(load-theme "monokai")

Example users' init files

• @sasanidas
• https://gist.github.com/jason-chandler/6332e3fd753fa87e3b1cd13582df5862 getting cxxxr/valtan to work along with paredit and the monokai theme