I spent the past few weeks using the evening and weekend to learn Haskell and research how I could use it to build a web app. Here’s the most interesting points I found:
Compared to Clojure
- Rich borrowed almost all of Clojure’s standard library from Haskell.
- Destructuring in Clojure also looks like it came directly from Haskell.
- Haskell’s pattern matching is so much more useful than Clojure’s core.match library.
- Haskell’s sum types are really indispensable, I really wish Clojure had them.
- Static typing acts like free unit tests!
- Type inference means you almost never have to specify a type, so it feels as limber as dynamic typing.
- You can use the
$operator to avoid parentheses. So
foo quux (bar baz)can become
foo quux $ bar baz.
- All functions are curried, so there’s no need for Clojure’s
- You can make your own operators, with their own precedence and associativity.
- Type classes are great for polymorphism, and can also define operators (like Eq and Ord do).
Uses for monads
- They make sequential operations much less ugly while working in a purely-functional language.
- They can be used to separate interface from implementation.
- They make error propagation much simpler. In almost all cases, you can use the Either or Maybe monads to replace exceptions.
- A lot of what they call EDSLs (like Clay, Lucid, Scotty, etc.) are made using monads.
- I love Haskell’s syntax in theory, but real-world code is kind of hard for me to read. Maybe it just takes time like it did with Clojure.
- We have to pay attention to operator precedence once again.
- The tooling around Haskell isn’t as good as in the Clojure ecosystem, but it’s not that far off.
- The “do” syntactic sugar for chaining monads can trick you into thinking you’re writing imperative code. This confused me at first.
- Records (like
defrecord) can’t use a field name that’s already been used within another record in the same namespace.
- Monads still confuse me a lot, even though I think I understand them.
- There’s such a thing as “Monad Transformers” which sound even scarier than Monads to me. I’ve yet to even look into them.
- Compiling a Haskell project is about as slow as compiling a Clojure project.
- I really don’t like lazy IO. But it’s not related to non-strict evaluation, so it’s very much an opt-in feature that I just wouldn’t use.
Some interesting libraries
- Clay: library to generate CSS, like Garden.
- Lucid: library to generate HTML, like Hiccup.
- Hspec: RSpec clone.
- Scotty: just like Compojure, built on top of WAI, the Haskell equivalent to Ring.
- Aeson: JSON library, but serves a similar purpose as Prismatic’s Schema.
Anyway, just some thoughts on Haskell. It looks really cool, but I’m still undecided on whether I want to actually write a real-world app in Haskell.
My name is Steven Degutis, and I've been writing software professionally for a decade. During that time, I've written many apps and websites, quite a few technical articles, and kept up-to-date with the rapidly evolving software industry.
If you have software needs for web, mobile, or desktop, and are looking for a seasoned software professional, please reach out to me at firstname.lastname@example.org to set up a phone call.
- Self-employed – present
- Clean Coders – 5 years
- 8th Light – 2 years
- Big Nerd Ranch – 1 year
- Self-employed - 1 year
- Web: full-stack
- iOS (UIKit)
- macOS (Cocoa)
- REST APIs
- AWS / EC2 / ELB
- HTML5 / CSS
Over the past decade, I've written a total of 172 technical articles on various programming languages, frameworks, best practices, and my own projects, as I kept up-to-date and active in the software industry.
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- 2017 — "Clean code" isn't actually clean
- 2017 — Passion in your field is overrated
- 2017 — What I learned in 5 days of writing an experimental website
- 2014 — Age of the Polyglot
- 2013 — How to Program
- 2013 — Ignore the Naysayers
- 2013 — Writing Clearly
- 2012 — Reinvent the wheel
- 2010 — Good usability
- 2009 — Twitter is the wrong tool
- 2009 — We're all pretty bad at driving
- 2008 — Why I Code
|August||NDD: Narrative Driven Development|
|August||The truth about TDD|
|August||Macroframeworks vs Microframeworks|
|March||Notes on Haskell Extensions|
|February||Second thoughts on front-end tools|
|February||First thoughts on front-end tools|
|February||Some thoughts on GUIs|
|February||First thoughts on OCaml|
|February||First thoughts on Haskell|
|August||Age of the Polyglot|
|August||The history of Mjolnir|
|August||Quitting the GUI wars|
|June||Lua: my new favorite extension language|
|January||My programming life-goals|
|January||Lingua Latina, Pars I|
|January||Allocating an AST on the stack|
|April||Ruby Accessors Considered Pernicious|
|March||Reinvent the wheel|
Here are some of the projects I'm most proud of. They were created using a variety of technologies, running on several different platforms and OSes. They're all finished products, and many of them are open source.
I made Docks in 2009 for users who wanted to swap out icons in their Dock with a single click. Its unique functionality and design aesthetic attracted the attention of Apple, Engadget, MacWorld, and led to an acquisition of my start-up by Big Nerd Ranch.
This toy was made in a weekend to entertain my 1 year old daughter. It lets you create bubbles with your fingers, which then simulate physics by bumping into each other and falling.
When I couldn't find an app in the App Store that let me make very simple lists extremely quickly, I made one myself. I use it almost every day to organize and track my activities.
I created this app to increase my productivity by letting me move windows around in macOS using keyboard shortcuts. It grew into a community-driven highly extensible app, using Lua for its plugin system.
Implementing this elite social network gave me experience integrating both Apple Pay and credit card payments (via Stripe.com) seamlessly into web apps, for a frictionless and pain-free payment experience.
This isn't just any chatroom. In this web app, you can see what everyone is typing while they type it. I made this in order to scratch my itch for making real-time apps and games, and learned how to use WebSockets in the process.
This was written in 2009, before the time of Slack, when IRC was the main way for programmers to get short-term assistance from each other. Its purpose was to be a beautiful app with an emphasis on simplicity and usability over technical power.
This is an app I actually use every single day. It lets you move windows with global keyboard shortcuts. Since it uses Vim-like key bindings, it should feel pretty natural to any programmer. There's no configuration needed; it Just Works™.
As an evolution of Phoenix, Hydra was my first attempt at embedding a full Lua virtual machine into an Objective-C app, to make a lightweight and efficient window manager that focused on speed, low memory usage, low CPU usage, and overall being gentle on laptop batteries.
These may be tiny, but they're interesting technical feats.
|Lua4Swift||Swift framework for embedding Lua with a native Swift API.|
|choose||Command line fuzzy-matching tool for macOS that uses a GUI|
|music||Command line music daemon for macOS that only speaks JSON|
|hecto||Command line text editor with an embedded Lua plugin system|
|ZephSharp||Window manager for Windows using Clojure for scripting|
|management||Minimalist EC2 configuration & deployment tool in Ruby.|
|go.assert||Assertion helper package for writing tests in Go.|
|go.shattr||Go library for printing shell-attributed strings to stdout.|
|OCDSpec2||Objective-C based testing framework with Xcode integration.|