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@vasanthk
vasanthk / System Design.md
Last active October 18, 2025 10:20
System Design Cheatsheet

System Design Cheatsheet

Picking the right architecture = Picking the right battles + Managing trade-offs

Basic Steps

  1. Clarify and agree on the scope of the system
  • User cases (description of sequences of events that, taken together, lead to a system doing something useful)
    • Who is going to use it?
    • How are they going to use it?
@macmade
macmade / cpp-fibs.cpp
Created June 11, 2015 22:20
C++ Fibonacci
#include <iostream>
template< int N >
struct Fibonacci
{
static constexpr int value = Fibonacci< N - 1 >::value + Fibonacci< N - 2 >::value;
};
template<>
struct Fibonacci< 1 >
@non
non / answer.md
Last active February 28, 2025 11:46
answer @nuttycom

What is the appeal of dynamically-typed languages?

Kris Nuttycombe asks:

I genuinely wish I understood the appeal of unityped languages better. Can someone who really knows both well-typed and unityped explain?

I think the terms well-typed and unityped are a bit of question-begging here (you might as well say good-typed versus bad-typed), so instead I will say statically-typed and dynamically-typed.

I'm going to approach this article using Scala to stand-in for static typing and Python for dynamic typing. I feel like I am credibly proficient both languages: I don't currently write a lot of Python, but I still have affection for the language, and have probably written hundreds of thousands of lines of Python code over the years.

Git DMZ Flow

I've been asked a few times over the last few months to put together a full write-up of the Git workflow we use at RichRelevance (and at Precog before), since I have referenced it in passing quite a few times in tweets and in person. The workflow is appreciably different from GitFlow and its derivatives, and thus it brings with it a different set of tradeoffs and optimizations. To that end, it would probably be helpful to go over exactly what workflow benefits I find to be beneficial or even necessary.

  • Two developers working on independent features must never be blocked by each other
    • No code freeze! Ever! For any reason!
  • A developer must be able to base derivative work on another developer's work, without waiting for any third party
  • Two developers working on inter-dependent features (or even the same feature) must be able to do so without interference from (or interfering with) any other parties
  • Developers must be able to work on multiple features simultaneously, or at lea
@14427
14427 / hkt.rs
Last active September 26, 2025 13:52
Higher-kinded type trait
use std::rc::Rc;
trait HKT<U> {
type C; // Current type
type T; // Type with C swapped with U
}
macro_rules! derive_hkt {
($t:ident) => {
impl<T, U> HKT<U> for $t<T> {
@djspiewak
djspiewak / streams-tutorial.md
Created March 22, 2015 19:55
Introduction to scalaz-stream

Introduction to scalaz-stream

Every application ever written can be viewed as some sort of transformation on data. Data can come from different sources, such as a network or a file or user input or the Large Hadron Collider. It can come from many sources all at once to be merged and aggregated in interesting ways, and it can be produced into many different output sinks, such as a network or files or graphical user interfaces. You might produce your output all at once, as a big data dump at the end of the world (right before your program shuts down), or you might produce it more incrementally. Every application fits into this model.

The scalaz-stream project is an attempt to make it easy to construct, test and scale programs that fit within this model (which is to say, everything). It does this by providing an abstraction around a "stream" of data, which is really just this notion of some number of data being sequentially pulled out of some unspecified data source. On top of this abstraction, sca

Practical Cryptographic Release Branch Validation

One of the problems I've been thinking about recently is how to get reasonable cryptographic validation of release sources and artifacts without destroying usability. There are several randomly-assorted problems here:

  • SHA-1 is relatively easy to collide, and thus signed Git commits and tags are insufficient
  • Maintaining an auditable and relatively tamper-proof list of trusted signatures is hard
  • "Strong crypto" is generally (and accurately) equated with "not human usable"

Things to Sign

@paf31
paf31 / 24days.md
Last active August 8, 2023 05:53
24 Days of PureScript

This blog post series has moved here.

You might also be interested in the 2016 version.

@paf31
paf31 / node-haskell.md
Last active May 14, 2024 03:51
Reimplementing a NodeJS Service in Haskell

Introduction

At DICOM Grid, we recently made the decision to use Haskell for some of our newer projects, mostly small, independent web services. This isn't the first time I've had the opportunity to use Haskell at work - I had previously used Haskell to write tools to automate some processes like generation of documentation for TypeScript code - but this is the first time we will be deploying Haskell code into production.

Over the past few months, I have been working on two Haskell services:

  • A reimplementation of an existing socket.io service, previously written for NodeJS using TypeScript.
  • A new service, which would interact with third-party components using standard data formats from the medical industry.

I will write here mostly about the first project, since it is a self-contained project which provides a good example of the power of Haskell. Moreover, the proces

@david-christiansen
david-christiansen / FizzBuzzC.idr
Last active August 29, 2022 20:00
Dependently typed FizzBuzz, now with 30% more constructive thinking
module FizzBuzzC
%default total
-- Dependently typed FizzBuzz, constructively
-- A number is fizzy if it is evenly divisible by 3
data Fizzy : Nat -> Type where
ZeroFizzy : Fizzy 0
Fizz : Fizzy n -> Fizzy (3 + n)