Patrick Pijnappel, Developer in Melbourne, Victoria, Australia
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Patrick Pijnappel

Verified Expert  in Engineering

Software Developer

Melbourne, Victoria, Australia
Toptal Member Since
February 10, 2016

Patrick has been deeply passionate about programming since the age of 12. He is a longtime freelancer, co-founder of Archimedes, and a contributor to experimental AI research and the Swift language itself. He thrives on the really hard problems, clean architecture and advanced performance optimization. He has coded in over a dozen different languages and can pick up new languages and technologies very quickly.



Preferred Environment

Git, Xcode, MacOS

The most amazing...

...thing I've developed is a next-generation graphing calculator with custom mathematical typesetting and custom symbolic solving engine.

Work Experience


2011 - 2018
Archimedes Calculator
  • Designed and developed Archimedes, a next-generation graphing calculator for iOS.
  • Created a unique, fully-interactive mathematical typesetting system with fluid animation.
  • Wrote a custom symbolic math solving engine with automatic unit handling.
  • Implemented high-quality plotting functionality including smooth touch-based scroll/zoom, automatic POI detection, and direct-interaction tracing, differentiation, and integration tools.
  • Began developing an advanced experimental new type of symbolic math engine.
Technologies: iOS, Objective-C, Swift


2016 - 2017
  • Developed a location-based video sharing platform.
  • Figured out a way to have a performant feed of up to 16 simultaneously playing streaming video tiles.
  • Wrote frameworks for declarative endpoint specification, futures/promises, model parsing, model persistence, and change notification.
Technologies: AVFoundation, Node.js, Swift

Arduino/iOS Developer

2011 - 2017
DKP Veterinary Clinic
  • Created the software for a wifi-enabled advanced experimental operating table with Arduino-controlled electronics and an iPad interface.
  • Created the software for an experimental network of veterinary animal cells with lighting, heating, ventilation, and oxygen supply systems controlled by a distributed set of Arduinos communicating with an iPad interface.
  • Wrote a robust communication layer between a network of Arduinos and iOS devices using a simultaneous mixture of serial, I2C, and wifi channels.
  • Interfaced with a large number of different analog and digital sensors and actuators over a variety of different protocols.
  • Created a messaging system for generically binding sensors and settings on Arduinos to properties on iOS devices, automatically managing communication over a mixed channel network.
Technologies: iOS, Swift, Objective-C, Arduino, C++

iOS Developer

2015 - 2016
  • Created an iOS front-end app for a dynamic CRM application.
  • Wrote encapsulation for communication with a legacy REST back-end with consistent error handling.
  • Created dynamic UI for display and manipulation of records with arbitrary fields of different data types.
  • Created a self-contained encapsulation of a complex workaround for broken call tracking API.
  • Created dynamically fetching browse and search functionality for working with large record sets.
Technologies: iOS, Swift

Java Developer

2011 - 2011
  • Developed the third version of a leading forensics application for the measurement of suspects by joining camera images with point cloud data from 3D laser scans of the crime scene.
  • Completely transformed a large, undocumented old codebase into a clean, stable, and organized one.
  • Wrote code for 3D navigation, rendering, and manipulation using OpenGL.
  • Wrote code to load, manipulate, and render large datasets in a performant way.
  • Redesigned, localized, and generally modernized the UI.
Technologies: OpenGL, C, Java

Swift Standard Library
l've been one of the top non-Apple contributors to the Swift language and standard library since it became open-source. I primarily do performance optimization, rewrites, and spotting of edge cases in the standard library. Some of the more interesting ones include and

A next-generation scientific calculator with custom smoothly animated mathematical typesetting, lots of custom UI, and a custom symbolic math engine underneath.

Graduation project on an OS X application for the design of Arduino programs using finite state machines, including live runtime visualization of the executing Arduino code (Objective-C).
2011 - 2013

Master's (with Honors) Degree in Design for Interaction

Delft University of Technology - Delft, The Netherlands

2007 - 2010

Bachelor's Degree in Aerospace Engineering

Delft University of Technology - Delft, The Netherlands


OpenGL, GNU Multiple Precision (GMP), Node.js, XNA


Xcode, Git, Adobe Photoshop, Adobe Illustrator


Cocoa Touch, Windows Presentation Foundation (WPF), Cocoa, .NET, Express.js


iOS, Arduino, MacOS


Objective-C, Swift, Java, C, C#, Python, JavaScript, CSS, HTML, C++




Computer Graphics, AVFoundation

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