Ankit Gadiya

1767277502

2026-01-01T19:55:02+00:00

Happy New Year 🎉

New year, new instance. I'm changing the base domain for my single-user GoToSocial instance (by migration). If it worked, you shouldn't notice it.

social.argp.in</a> -> social.argp.org</a>.

My Emacs Presentation Stack

2025-11-30T00:00:00+00:00

This is my (last minute) submission for Emacs Carnival 2025-11 — An Ode to Org Babel</a>.

When I need to do presentations at work, I naturally reach for Emacs. My presentations include diagrams, code snippets and running small shell blocks. I found that Org Mode with Babel is the perfect fit. In this post, I'll describe my presentation stack based on Org mode.

Here is a quick demo video: Your browser does not support the video tag. </video>

Base — Org mode</h2>
I like to plan my presentations using outlines. It is easy to structure the presentation into sections and sub-sections. Outlines also let me easily reorganize parts of the presentation. I don't think outlines are standard features in common presentation software. But Emacs comes with a great outline package, Org Mode</a>. This is a subset of my configuration to make the presentations pretty.
(use-package org :hook ;; Lets me use serif for text and monospace for code snippets. (org-mode . variable-pitch-mode) :custom (org-hide-emphasis-markers t) (org-pretty-entities t) (org-ellipsis "…") (org-src-fontify-natively t) (org-src-tab-acts-natively t) (org-src-preserve-indentation t)) </code></pre>
I start with an empty Org mode file and write the outline for my presentation using Org mode headings. Each heading (and sub-heading) becomes a slide title. I use the Logos</a> package to present the Org file as slides. Logos uses Outline headings as page endings, and uses narrowing to only show the content under that heading. Logos in turn integrates with the Olivetti</a> package to center the content on the screen. This is the glue code to make it all work together.
(use-package logos :ensure t :init ;; Always expand the current Heading. (defun arg-reveal-entry () "Reveal Org or Outline entry." (cond ((and (eq major-mode 'org-mode) (org-at-heading-p)) (org-show-entry)) ((or (eq major-mode 'outline-mode) (bound-and-true-p outline-minor-mode)) (outline-show-entry)))) :custom (logos-outlines-are-pages t) (logos-olivetti t) :hook (logos-page-motion . arg-reveal-entry) :bind ;; Binds Logos functions for Page motions. (:map org-mode-map ([remap forward-page] . logos-forward-page-dwim) ([remap backward-page] . logos-backward-page-dwim)) :config ;; Disable distracting elements during Focus mode. (setq-default logos-hide-mode-line t logos-hide-header-line t)) (use-package olivetti :ensure t :config ;; Fancy mode uses margins and fringes to create vertical ;; blocks on either sides of the content. (setq olivetti-style 'fancy) (setq-default olivetti-body-width 0.4) (add-hook 'olivetti-mode-on-hook (lambda () ;; Disable Line numbers. (display-line-numbers-mode -1) ;; Disable Buffer boundaries. (setq-local indicate-buffer-boundaries nil))) (add-hook 'olivetti-mode-off-hook (lambda () ;; Enable Line numbers. (display-line-numbers-mode 1) ;; Restores Buffer boundaries. (setq-local indicate-buffer-boundaries 'left)))) </code></pre> I have the arg-start-presentation</code> and arg-stop-presentation</code> commands to toggle the presentation mode. In presentation mode, logos-focus-mode</code> is toggled with the current heading expanded. It also minimizes other elements of the Emacs frame like Tab-bar, and Menu-bar. To move between the slides, I use the Emacs page motion keybindings: Forward C-x ]</kbd>, and Backward C-x [</kbd>.
(defun arg-start-presentation () "Start Presentation - Configures Frame, Style, etc." (interactive) (when (eq major-mode 'org-mode) (setq-local arg-presentation t) (logos-focus-mode 1) (logos-narrow-dwim) (org-fold-show-entry) (toggle-frame-tab-bar (selected-frame)) (menu-bar-mode -1))) (defun arg-stop-presentation () "Stop Presentation - Reverts Frame, Style, etc." (interactive) (cond ((not (eq major-mode 'org-mode)) (error "This command only works in Org buffers.")) ((not arg-presentation) (error "Not presenting right now.")) (t (progn (logos-focus-mode -1) (widen) (toggle-frame-tab-bar (selected-frame)) (setq-local arg-presentation nil) (menu-bar-mode +1))))) </code></pre>
This setup is inspired by System Crafter's Presentation style</a>.
Magic — Org Babel</h2>
Org mode comes with built-in support for literate programming, Org Babel. If you're familiar with Jupyter Notebooks, Org Babel is a bit like that but in my opinion, Babel is more powerful and extensible. It supports most common languages out of the box such as Python, shell, and SQL, and it can be extended to work with almost any language using simple Emacs lisp functions. It also supports using multiple languages in the same file.
Diagrams</h3>
To add diagrams to my presentations, I like to use Pikchr</a>. It is a special purpose markup language for diagrams. Org mode allows me to define diagrams in-line right next to the slide content using code blocks.
Using Org Babel, I can compile the diagram using C-c C-c</kbd>. The generated SVG is placed directly in the buffer using the RESULTS</code> block. Org mode can optionally render the SVG in-line as well using C-c C-x C-v</kbd> or M-x org-toggle-inline-images</kbd>. Updating the diagrams is also straightforward: I can edit the code block and recompile the diagram to update the SVG. There is no hassle of exporting and importing the diagrams repeatedly.
#+begin_src pikchr :file hello.svg box "Hello!" #+end_src #+RESULTS: [[file:hello.svg]] </code></pre> Shell Execution</h3> If I have to present some shell commands, I add the Shell code blocks. Org Babel supports tons of options for shell. Some options that I use are: :results</code> – How the result is parsed. If the output is tabular, Org mode can display it as a table, otherwise verbatim.</li> :async</code> – If the command takes time, run it asynchronously without blocking Emacs.</li> :dir</code> – Sets the default directory for the Shell block.</li> </ul> For live demos, I add the shell blocks directly in my slide content. During the presentation, I can simply execute the block using C-c C-c</kbd>. This helps me focus on my content, saves time and I can avoid embarrassing typos. In case of pre-recorded commands, I execute the commands beforehand. Similar to diagrams, Org mode places the output of the command in the RESULTS</code> block. This is convenient when the commands require external setup, or take longer to run. Here is an example from my last presentation. #+begin_src shell :results output docker images --format "{{.Size}}\t{{.Repository}}" #+end_src #+RESULTS: : 8.31MB alpine : 120MB debian : 2.33GB ros </code></pre> Version Control</h2> Because Org mode uses plain text format, I can version control my presentations. It is one of those features that you'll appreciate when you use it. I put all my presentations along with the SVG artifacts in a single Git repository. A nice little bonus is that Github and Forgejo can also render Org markup. So I have a webpage complete with table of contents for my slides for free!

Church Booleans 2025-11-24T00:00:00+00:00 In the last post, I covered the basics of Lambda calculus</a> and its lack of built-in data types. Church encoding defines a way to represent data types as pure functions. In this post, I'll explore church booleans and control flow, and implement them using Python. Booleans as functions</h2> Booleans are plain functions that take two arguments. true</code> always returns the first argument,</li> false</code> always returns the second argument.</li> </ul> 𝛌a.𝛌b a # True 𝛌a.𝛌b b # False </code></pre> In Python, I can define these two functions for booleans. def true(a, b): return a def false(a, b): return b true(1, 2) # -> 1 false(1, 2) # -> 2 </code></pre> To understand why this works more clearly we'll look at control flow. Control flow constructs in Python</h2> In Python, if</code> is a special language construct that looks like this: if TRUE: BRANCH 1 else: BRANCH 2 </code></pre> Why can't it be a function? I'll try to define if</code> as a function using the boolean functions. def bad_if(bool_func, b1, b2): return bool_func(b1, b2) </code></pre> If the implementation is correct, it must evaluate exactly one branch. To check this, I'll call the bad_if</code> function with two branches. >>> bad_if(false, 2+2, 2-2) 0 >>> bad_if(true, 2+2, 2-2) 4 </code></pre> At first glance it looks correct. But we need to make sure that Python isn't evaluating both branches. I'll call bad_if</code> with two print</code> statements instead. >>> bad_if(true, print("Branch 1"), print("Branch 2")) Branch 1 Branch 2 </code></pre> This shows that Python did actually evaluate both branches. This happens because Python eagerly evaluates the arguments before the function call. It then passes the value of the evaluation to the function. So the bad_if</code> call is equivalent to this: b1 = print("Branch 1") # -> None b2 = print("Branch 2") # -> None bad_if(true, b1, b2) # -> None </code></pre> Because of the eager evaluation, Python needs a special syntax for control flow to avoid accidentally evaluating both branches. Conditionals in Lambda Calculus</h2> In contrast to Python's eager evaluation, Lambda calculus only evaluates the arguments when β-reduction</a> requires the value. So a function call similar to bad_if</code> behaves very differently in Lambda calculus. bad_if(true, print("Branch 1"), print("Branch 2")) true(print("Branch 1"), print("Branch 2")) # Reduce bad_if print("Branch 1") # Reduce true, returns first argument. </code></pre> Because of lazy evaluation, if the argument is not used then it will not be evaluated. So, we can define if</code> as a pure function in Lambda calculus. 𝛌f.𝛌a.𝛌b (f a b) </code></pre> To force lazy evaluation in Python, we can wrap the branches in a Lambda. We can then call the functions returned by the boolean function. def good_if(bool_func, b1, b2): # Notice we are calling the result from bool_func. return bool_func(b1, b2)() </code></pre> I'll call the good_if</code> with two branch lambdas. We can see that it correctly evaluates exactly one branch. >>> good_if(true, lambda: print("branch 1"), lambda: print("branch 2")) branch 1 >>> good_if(false, lambda: print("branch 1"), lambda: print("branch 2")) branch 2 </code></pre> Conclusion</h2> Church encoding shows how expressive Lambda calculus can be, and how higher-level constructs can be built from regular functions. There's much more to explore in future posts. Lambda Calculus 2025-11-17T00:00:00+00:00 Many modern programming languages trace their roots back to Lisp, which in turn builds on ideas from lambda calculus. In this post, I explore the core ideas of lambda calculus. What is lambda calculus</h2> For the longest time, I had the impression that lambda calculus has something to do with the calculus from high school mathematics. I was wrong, calculus here simply means to calculate. Lambda calculus is a system to define any computation. Think of it like an abstract programming language to express programs. It does so using simple ideas: variables, functions and their application. Basic constructs</h2> Lambda calculus defines two basic constructs. These are sufficient to model any computation. Variables Variables are symbols that act as identifiers in the computation. Variables can be free or bound to a function's scope (parameter). x # x is free </code></pre> But the variables don't behave like programming languages. So, you cannot assign values to them. </li> Functions Functions take arguments and perform some computation. The arguments are bound variables in the function's scope. This is a simple function that takes one argument x</code> and returns it. 𝛌y. y # y is bound </code></pre> Sidenote: A function can only take a single argument. But multiple arguments can be simulated by defining nested functions. 𝛌y.𝛌z y </code></pre> </li> </ul> Function application and β-reduction</h2> Functions are not useful on their own. To use the functions, you can apply them to arguments. Lambda calculus defines how functions are computed: β-reduction. β-reduction is a fancy term for repeated substitution. The functions are computed by progressively substituting bound variables within the function body. This is a contrived example to visualize β-reduction properly. Here is a nested function that takes two arguments and by repeated substitution, we get the result. (𝛌x.𝛌y. x) A B (𝛌y. A) B # First reduction for outer function. A # Second reduction for inner function. </code></pre> Conclusion</h2> That's it, there is no construct for conditionals, data types, loops etc. But curiously, it is possible to encode high-level constructs using these basic ideas. In a future post, I'll explore church encodings to encode conditionals and integers in lambda calculus. 1763127234 2025-11-14T19:03:54+00:00 I use the org-pomodoro</a> package for focused sessions at work. But Slack notifications can easily break my flow, so I added the simple hooks to disable visible notifications on GNOME desktop. (defun arg-disable-gnome-notifications () (shell-command "gsettings set org.gnome.desktop.notifications show-banners false")) (defun arg-enable-gnome-notifications () (shell-command "gsettings set org.gnome.desktop.notifications show-banners true")) (add-hook 'org-pomodoro-started-hook #'arg-disable-gnome-notifications) (add-hook 'org-pomodoro-finished-hook #'arg-enable-gnome-notifications) (add-hook 'org-pomodoro-break-finished-hook #'arg-enable-gnome-notifications) (add-hook 'org-pomodoro-killed-hook #'arg-enable-gnome-notifications) </code></pre> 1760213248 2025-10-12T01:37:28+00:00 I found a couple of videos exploring the concept of refractive index — why light seems to slow down in different mediums. In the first, the creator reasoned intuitively that light doesn't really slow down. She built a simple home experiment to prove it, but the results showed the opposite. In the second, she set out to understand why those observations actually made sense. Does light actually slow down in water?</a></li> I don't know why light slows down in water</a></li> </ul> 1759668366 2025-10-05T18:16:06+00:00 I'm learning about lambda calculus, the mathematical foundation of Lisp. It defines an incredibly expressive system. The Church encodings finally clicked for me. Real-Time (Co)Maps While Flying 2025-10-04T00:00:00+00:00 Background</h2> On an international flight, I saw that the in-flight entertainment system had a navigation feature. It shows a map with the source and destination, along with the plane's real-time location. It felt like a moving progress bar and also gave me a sense of the geography I was flying over. But a lot of budget airlines or domestic flights don't offer an in-flight entertainment system. I can't use Google Maps or Apple Maps because it requires an active internet connection. I wished this feature were available on all flights. Then I accidentally discovered that Comaps could do exactly what I'd been missing. What is Comaps?</h2> Comaps</a> is an open-source navigation app similar to Google Maps and Apple Maps. The unique thing about it is that it can work completely offline. It lets you download map data from OpenStreetMap</a> for any regions you want. After downloading the maps, Comaps doesn't use the internet at all. It may sound surprising, it did to me, but GPS navigation doesn't need an internet connection. Smartphones come with built-in GPS modules that can communicate with the GPS satellites to figure out where you are on Earth. Use Comaps for in-flight navigation</h2> To use Comaps this way, download maps of all the regions on your flight's path before boarding the plane. Then during the flight, switch to airplane mode and you will still be able to use the map. As the plane moves through the sky, your pointer will move along with it. Comaps is better than the in-flight system because the map is interactive. Zooming in on the cities and spotting landmarks feels way more fun than staring at a tiny seat-back screen. 1759417306 2025-10-02T20:31:46+00:00 TIL that in Magit buffers, pressing \</kbd> (or M-x evil-collection-magit-toggle-text-mode</code>) activates text-mode</code>. This mode enables standard visual motions that are unavailable in Magit buffers. Implement Custom Tramp Method in Emacs 2023-09-27T00:00:00+00:00 Emacs supports editing remote files using the Tramp package. Emacs transparently handles the remote files based on the special path prefixes specified, so the experience is similar to operating on a local file. Tramp uses a remote shell underneath to access remote files. In this article, I'll talk about how to extend Tramp to support custom Methods to access remote files. XMLRPC 2021-03-11T00:00:00+00:00 In this article, I'll talk about a pretty old RPC Protocol, XMLRPC. It is over 20 years old now and, it is mostly associated in legacy systems. I'd have never come across it if it wasn't for ROS. ROS 1.x still uses XMLRPC for all of its communication. So, I decided to read out the protocol specification. Introduction to ROS 2021-03-04T00:00:00+00:00 ROS is an acronym for Robot Operating System, but contrary to the name it is not an operating system. Instead, ROS is an open-source framework for building software for Robots. I got introduced to ROS in my current company which is a Cloud Robotics startup. In this article, I'll give a general introduction to ROS based on what I learned. Selfhosting 2021-02-11T00:00:00+00:00 In this article, I'll share my thoughts about Selfhosting. Bitwarden RS 2020-09-28T00:00:00+00:00 I’ve been a happy user of Bitwarden for over a year. In this article, I’ll talk about an alternate implementation of Bitwarden and my experience with it. Pitfalls of Gorm: Unique Index 2020-09-01T00:00:00+00:00 Gorm is a popular ORM library in Golang that supports the most commonly used Relational Databases. In this article, I want to talk about a subtle problem in the unique index support for Gorm.… Redlock 2020-07-06T00:00:00+00:00 Salvatore Sanfilippo described an algorithm using Redis to implement distributed locking called Redlock. In this article, we will talk about this algorithm. The Strange case of Golang's Append 2020-01-02T00:00:00+00:00 Today while working on a Golang code-base at work, I came across an anomaly, or at least that's what I thought.… Vanity Imports in Golang 2019-12-25T00:00:00+00:00 The imports in Golang are the full path of the package including the domain name. It is common to host the packages on Github and use it for import as well. However, there are two problems with it. Backup SQLite 2019-12-22T00:00:00+00:00 SQLite is one of the most popular embedded relational database. The SQLite native libraries or language bindings are available for most popular languages. SQLite files can be accessed either interactively or using shell scripts using the command-line utility. Federated Git 2019-12-17T00:00:00+00:00 Git is a Distributed Version Control System or DVCS, created for the Linux Kernel project. The idea behind a DVCS is that there is no concept of central repository. Every copy (clone) has all the information. But generally, there is a central repository that acts as a single source of truth for all the developers.… Switched from Pocket to Instapaper 2019-12-16T00:00:00+00:00 I started using Pocket in 2018, and since then, I became one of the top 5% of there user-base (according to one email I received). But recently, I decided to switch to Instapaper. I had several reasons for making the move that I'll talk about in this post. Miniflux 2019-12-15T00:00:00+00:00 I had used multiple Atom/Feed Readers in the past, including command-line based Newsbeuter (and Newsboat), Elfeed as part of Emacs and Reeder on Mac OS. But, my main problem was that none of them support syncing to my Android phone. There is also no integration with Instapaper.

Conclusion</h2>
Church encoding shows how expressive Lambda calculus can be, and how higher-level constructs can be built from regular functions. There's much more to explore in future posts.</p>

Ankit Gadiya

1767277502

My Emacs Presentation Stack

Church Booleans

Lambda Calculus

Conclusion</h2>
That's it, there is no construct for conditionals, data types, loops etc. But curiously, it is possible to encode high-level constructs using these basic ideas. In a future post, I'll explore church encodings</em> to encode conditionals and integers in lambda calculus.</p>

1763127234

1760213248

1759668366

Real-Time (Co)Maps While Flying

1759417306

Implement Custom Tramp Method in Emacs

XMLRPC

Introduction to ROS

Selfhosting

Bitwarden RS

Pitfalls of Gorm: Unique Index

Redlock

The Strange case of Golang's Append

Vanity Imports in Golang

Backup SQLite

Federated Git

Switched from Pocket to Instapaper

Miniflux

Ankit Gadiya

1767277502

My Emacs Presentation Stack

Church Booleans

Booleans as functions</h2> Booleans are plain functions that take two arguments.</p> true</code> always returns the first argument,</li>

Control flow constructs in Python</h2> In Python, if</code> is a special language construct that looks like this:</p>

Conclusion</h2> Church encoding shows how expressive Lambda calculus can be, and how higher-level constructs can be built from regular functions. There's much more to explore in future posts.</p>

Lambda Calculus

Conclusion</h2> That's it, there is no construct for conditionals, data types, loops etc. But curiously, it is possible to encode high-level constructs using these basic ideas. In a future post, I'll explore church encodings</em> to encode conditionals and integers in lambda calculus.</p>

1763127234

1760213248

1759668366

Real-Time (Co)Maps While Flying

1759417306

Implement Custom Tramp Method in Emacs

XMLRPC

Introduction to ROS

Selfhosting

Bitwarden RS

Pitfalls of Gorm: Unique Index

Redlock

The Strange case of Golang's Append

Vanity Imports in Golang

Backup SQLite

Federated Git

Switched from Pocket to Instapaper

Miniflux

Conclusion</h2>
Church encoding shows how expressive Lambda calculus can be, and how higher-level constructs can be built from regular functions. There's much more to explore in future posts.</p>

Conclusion</h2>
That's it, there is no construct for conditionals, data types, loops etc. But curiously, it is possible to encode high-level constructs using these basic ideas. In a future post, I'll explore church encodings</em> to encode conditionals and integers in lambda calculus.</p>