HomeAboutPostsTagsProjectsRSS

Updated
Words908
TagsRead3 minutes

typical usage of result.unwrap and result.or

result.unwrap and result.or are both useful functions in Gleam for working with Result types, but they serve different purposes.

result.unwrap

result.unwrap is used to extract the value from a Result, providing a default value if the Result is an Error. It’s typically used when you want to proceed with a default value rather than propagating an error.

Typical usage:

import gleam/result

pub fn get_user_name(user_id: Int) -> Result(String, Nil) {
  // Simulated user lookup
  case user_id {
    1 -> Ok("Alice")
    2 -> Ok("Bob")
    _ -> Error(Nil)
  }
}

pub fn greet_user(user_id: Int) -> String {
  let name = get_user_name(user_id)
    |> result.unwrap("Guest")

  "Hello, " <> name
}

// Usage:
pub fn main() {
  io.println(greet_user(1))  // Prints: "Hello, Alice"
  io.println(greet_user(3))  // Prints: "Hello, Guest"
}

In this example, result.unwrap allows us to use a default value (“Guest”) when the user lookup fails, ensuring that we always have a name to greet.

result.or

result.or is used to provide an alternative Result when the first Result is an Error. It’s typically used when you have a fallback operation or value that you want to try if the primary operation fails.

Typical usage:

import gleam/result

pub fn get_config_from_file() -> Result(Config, String) {
  // Simulated file read
  Error("File not found")
}

pub fn get_default_config() -> Result(Config, String) {
  // Return a default configuration
  Ok(Config(..))
}

pub fn get_config() -> Result(Config, String) {
  get_config_from_file()
  |> result.or(get_default_config())
}

// Usage:
pub fn main() {
  case get_config() {
    Ok(config) -> io.println("Config loaded")
    Error(err) -> io.println("Failed to load config: " <> err)
  }
}

In this example, result.or allows us to try loading the configuration from a file first, and if that fails, fall back to using a default configuration. The get_config function will only return an Error if both operations fail.

Key differences and when to use each:

  • Use result.unwrap when you want to extract a value from a Result and have a sensible default to use if it’s an Error. This effectively “throws away” the error information.
  • Use result.or when you want to try an alternative operation if the first one fails, while still preserving the Result type. This allows you to chain multiple fallback options.
  • result.unwrap returns the unwrapped value directly, while result.or returns another Result.
  • result.unwrap is often used at the “edges” of your program where you need to interface with code that doesn’t use Results, while result.or is more commonly used within the “core” logic where you’re still working with Results.

Both functions are valuable tools for error handling in Gleam, and understanding when to use each can lead to more robust and expressive code.

Rust

Same principle can be applied to Rust as the design is very alike.

Updated
Words204
TagsRead1 minute

Rust compilation failed on Apple Silicon Macbook

ld: symbol(s) not found for architecture arm64
clang: error: linker command failed with exit code 1 (use -v to see invocation)

Fix: [ld: symbol(s) not found for architecture x86_64 · Issue #15 · rochacbruno/rust-python-example · GitHub]( ld: symbol(s) not found for architecture x86_64 · Issue #15 · rochacbruno/rust-python-example · GitHub )

switch to rust nightly

rustup toolchain install nightly
cd <path/to/project>
rustup override set nightly

cargo rustc --release -- -C link-arg=-undefined -C link-arg=dynamic_lookup

Updated
Words1216
TagsRead2 minutes

Here is the most valuable part of my emacs vTerm config with fish shell.

add source vterm.fish to your fish shell configuration file

use edit <file> in vTerm buffer will open file at the new window above vTerm buffer, similar to using code <file> in VSCode embedded terminal.

vterm.fish

# https://github.com/akermu/emacs-libvterm
function vterm_printf
    if begin
            [ -n "$TMUX" ]; and string match -q -r "screen|tmux" "$TERM"
        end
        # tell tmux to pass the escape sequences through
        printf "\ePtmux;\e\e]%s\007\e\\" "$argv"
    else if string match -q -- "screen*" "$TERM"
        # GNU screen (screen, screen-256color, screen-256color-bce)
        printf "\eP\e]%s\007\e\\" "$argv"
    else
        printf "\e]%s\e\\" "$argv"
    end
end

function vterm_cmd --description 'Run an Emacs command among the ones been defined in vterm-eval-cmds.'
    set -l vterm_elisp ()
    for arg in $argv
        set -a vterm_elisp (printf '"%s" ' (string replace -a -r '([\\\\"])' '\\\\\\\\$1' $arg))
    end
    vterm_printf '51;E'(string join '' $vterm_elisp)
end

if [ "$INSIDE_EMACS" = vterm ]
    set -gx EDITOR code

    function clear
        vterm_printf "51;Evterm-clear-scrollback"
        tput clear
    end
    # used by vterm buffer name
    function fish_title
        hostname
        echo ":"
        prompt_pwd
    end

    function vterm_prompt_end --on-variable PWD
        vterm_printf '51;A'(whoami)'@'(hostname)':'(pwd)
    end

    function edit
        set -q argv[1]; or set argv[1] "."
        vterm_cmd vterm-edit-file (realpath "$argv")
    end
end

doom emacs config

config.el

(after! vterm
	(defun vterm-edit-file (file)
	    "Open a file from vterm in another window, keeping only the vterm window and the new file window."
	    (interactive)
	    (let ((current-vterm-window (catch 'found
	                                  (dolist (win (window-list))
	                                    (when (and (window-live-p win)
	                                               (eq 'vterm-mode (buffer-local-value 'major-mode (window-buffer win))))
	                                      (throw 'found win)))))
	          new-file-window)
	      (when current-vterm-window
	        ;; Open file in a new window from current VTerm window
	        (select-window current-vterm-window)
	        (setq new-file-window (split-window-below)) ; Adjust split direction to preference
	        (set-window-buffer new-file-window (find-file-noselect file))
	        ;; Delete all other windows except for VTerm and the new file window
	        (mapc (lambda (win)
	                (unless (or (eq win current-vterm-window)
	                            (eq win new-file-window))
	                  (delete-window win)))
	              (window-list))
	        (select-window new-file-window))))
	
	  (add-to-list 'vterm-eval-cmds '("vterm-edit-file" vterm-edit-file)))

Updated
Words595
TagsRead1 minute

Recently discovered Gleam language, and totally fell in love with it shortly!

Here is how you can setup Gleam in doom-emacs

packages.el

We just need the gleam-ts-mode.el, do not download gleam-mode.el as when it gets compiled it requires tree-sitter which causes problem.

(package! gleam-ts-mode
  :recipe (:host github
           :repo "gleam-lang/gleam-mode"
           :branch "main"

           :files ("gleam-ts-*.el")))

config.el

(use-package! gleam-ts-mode
  :config
  ;; setup formatter to be used by `SPC c f`
  (after! apheleia
    (setf (alist-get 'gleam-ts-mode apheleia-mode-alist) 'gleam)
    (setf (alist-get 'gleam apheleia-formatters) '("gleam" "format" "--stdin"))))

(after! treesit
  (add-to-list 'auto-mode-alist '("\\.gleam$" . gleam-ts-mode)))

(after! gleam-ts-mode
  (unless (treesit-language-available-p 'gleam)
    ;; compile the treesit grammar file the first time
    (gleam-ts-install-grammar)))

hack

If you, like me, use Treesitter grammar files from Nix, the tree-sitter subdirectory within the directory specified by user-emacs-directory is linked to Nix’s read-only filesystem, meaning gleam-ts-install-grammar is unable to install grammar files there.

Here’s how you can adjust treesit-extra-load-path and install the grammar file.

(after! gleam-ts-mode
  (setq treesit-extra-load-path (list (expand-file-name "~/.local/tree-sitter/")))
  (unless (treesit-language-available-p 'gleam)
    ;; hack: change `out-dir' when install language-grammar'
    (let ((orig-treesit--install-language-grammar-1 (symbol-function 'treesit--install-language-grammar-1)))
      (cl-letf (((symbol-function 'treesit--install-language-grammar-1)
                 (lambda (out-dir lang url)
                   (funcall orig-treesit--install-language-grammar-1
                            "~/.local/tree-sitter/" lang url))))
        (gleam-ts-install-grammar)))))

Updated
Words205
TagsRead1 minute

Just learned that using [[Emacs]], press C-\ to set input method to TeX, then input Greek symbols will be very easy, for example type \theta will display θ

Here are some frequently used symbols when writing math equations.

symbol
\alphaα
\thetaθ
\delta
Δ
\nabla

Updated
Words590
TagsRead2 minutes

In macOS, I’ve configured a variety of shortcuts to automate tasks, for example:

  • Appending selected text to a specified Obsidian note.
  • Opening a prompt menu and sharing the selected text with ChatGPT to obtain results.
  • Extracting text from an image to read in an editor.
  • And many others.

I frequently use these actions on both my iPhone and Mac. However, on macOS, I find myself having to manually navigate through the Services menu to activate these actions, which tends to slow down my workflow.

To streamline this process, I’ve developed a script that automatically triggers a Services menu item whenever I select text and press Command + Right Click. This enhancement significantly speeds up my interaction with macOS, making my workflow more efficient.

[[Hammerspoon]] script

-- Ensure the listener is global to avoid garbage collection issues
MouseListener = hs.eventtap.new({ hs.eventtap.event.types.rightMouseDown }, function(e)
  local buttonPressed = e:getProperty(hs.eventtap.event.properties.mouseEventButtonNumber)
  local cmdPressed = e:getFlags().cmd

  if cmdPressed == true then
    -- AppleScript to open the Services menu
    -- https://stackoverflow.com/a/59330902/22903883
    hs.osascript.applescript([[
tell application "System Events"
    set appName to item 1 of (get name of processes whose frontmost is true)
    tell (process 1 where frontmost is true)
        tell menu bar 1
            tell menu bar item appName
                tell menu appName
                     tell menu item "Services"
                          tell menu "Services"
                            click menu item "GPT: Share"
                          end tell
                     end tell
                end tell
            end tell
        end tell
    end tell
end tell]])
    return true -- Consume the right-right-click
  end

  return false
end)

-- Start the event listener
MouseListener:start()

Updated
Words655
TagsRead2 minutes

Using lsp-bridge for Language Server Protocol in Emacs

Emacs 29 introduced built-in TRAMP Docker support for editing files within containers. However, enabling auto-completion inside a container remains challenging.

After discovering lsp-bridge , I realized the benefit of a Python process interacting with the language server, rather than relying solely on Emacs Lisp.

I added a feature for automatic reconnection to remote SSH servers and started supporting devcontainers. Using nix-darwin to configure my MacBook, I implemented the devcontainer feature to install lsp-bridge and the language server within the devcontainer. This was facilitated by the Nix ecosystem . To make it work, I needed to start with patching the official Nix devcontainer feature and create separate projects — a long journey, but worthwhile.

Container File Buffer Handling

When opening files in a container, lsp-bridge creates an lsp-bridge buffer, inserts the file content, and uses it for editing and rendering diagnostic information. The remote file content on the container is maintained by the lsp-bridge server running inside the container.

I completed the handling of the visited file modification time for the buffer and enabled auto-revert mode to reload file content automatically when the formatter updates the file.

Using the created lsp-bridge buffer, I used set-visited-file-name to associate a buffer with a file path. However, saving the buffer after the first save prompts a warning: “File has been changed since visited.” This occurs due to discrepancies in how file timestamps are handled by Emacs through TRAMP. To resolve this, Emacs’ record of the file’s modification time must be manually updated with something like this:

(defun my-update-file-mod-time ()
  (when buffer-file-name
    (let ((mod-time (file-attribute-modification-time (file-attributes buffer-file-name))))
      (set-visited-file-modtime mod-time))))

(add-hook 'after-save-hook 'my-update-file-mod-time)

Emacs’ “auto-revert” mode, which automatically reverts buffers when the displayed files change externally, is also useful when files are updated by the formatter. Therefore, the file buffer must enable auto-revert-mode.

With these pieces in place, I now have a smooth editing experience with auto-completion inside the devcontainer.

Emacs rocks!

Updated
Words95
TagsRead1 minute

When taking notes, friction is often a good thing. If it is too easy to create a new note, you don’t write something on your own, but rather just collect information. Consequently, your brain do not process the information, so you learn less from just collecting and reading it. Physical notes have a physical constraint and a limitation on how much we can write on them, but digital notes have no such limitation and rely on self-discipline. So, when taking notes, it is too easy to write too many words. Keep it short and simple.

Updated
Words288
TagsRead1 minute

I use vertico-postframe to place my completion window at the center of screen, however when doing incremental search like doom-emacs SPC s s, it will block the man window.

Here is how to temporarily disable vertico-posframe-mode in Emacs before executing a function, like an incremental search, and then re-enable it afterward.

(defun my-search-without-posframe ()
  "Perform a search without `vertico-posframe-mode' temporarily."
  (interactive)
  ;; Disable vertico-posframe-mode if it's enabled
  (when (bound-and-true-p vertico-posframe-mode)
    (vertico-posframe-mode -1)
    (unwind-protect
        ;; Perform the search
        (call-interactively '+default/search-buffer)
      ;; Re-enable vertico-posframe-mode
      (vertico-posframe-mode 1))))

in config.el

(map! :leader
      :desc "Search without posframe"
      "s s" #'my-search-without-posframe)

Updated
Words329
TagsRead1 minute

different height for Org mode headings

modify only the height of headings in Org mode without affecting other attributes like color

Instead of using custom-theme-set-faces which replaces the whole face definition (and could unintentionally override theme-specific settings like color), use set-face-attribute

doom-emacs config example

(after! org
  ;; Adjust the height of org headings upon org-mode startup
  (add-hook 'org-mode-hook (lambda ()
    (dolist (face '((org-level-1 . 1.75)
                    (org-level-2 . 1.5)
                    (org-level-3 . 1.25)
                    (org-level-4 . 1.1)
                    (org-level-5 . 1.05)
                    (org-level-6 . 1.0)
                    (org-level-7 . 0.95)
                    (org-level-8 . 0.9)))
      (set-face-attribute (car face) nil :height (cdr face)))))