Krzysztof Cieślak

Krzysztof Cieślak

Developer Tools Researcher, OSS contributor, FP enthusiast

Łódź, Poland

Krzysztof is a photographer, globetrotter, and public speaker. He works as a Principal Research Engineer at [GitHub Next](https://next.github.com/), where he designs and builds the next generation of developer tools such as [GitHub Copilot](https://copilot.github.com/) or [Copilot Voice](https://githubnext.com/projects/copilot-voice/)

After the work, Krzysztof is an open-source software maintainer passionate about functional programming (especially F#), editor tooling and developer experience - he has created and maintained several OSS projects varying from [language servers](https://github.com/fsharp/FsAutoComplete) to [web frameworks](https://github.com/SaturnFramework/Saturn) to [VSCode plugins](https://github.com/ionide/ionide-vscode-fsharp).

Additionally, he is a passionate public speaker. You can meet him at many conferences around the world, where he is always trying to meet new people and learn how to improve software developers' lives.

Area of Expertise

  • Information & Communications Technology


  • .NET
  • F#
  • Open Source Software
  • Web Development
  • Functional Programming
  • JavaScript
  • TypeScript
  • JavaScript Typescript
  • Developer Experience
  • Developer Tools
  • Artificial Intelligence

Bringing the power of AI to your application.

Artificial Intelligence (AI), and specifically Large Language Models (LLMs) such as GPT-4 from OpenAI, is taking over the software development world - more and more applications are trying to build integrations with those powerful models.
But how do those models work? Is their power as unlimited as it seems? How to communicate with AI and make sure it does what you need?

In this talk, you will get a practical introduction to the world of LLMs and the art and science of prompt crafting. You will learn how to use AI models, how to design efficient inputs to the model - called prompts - and what techniques you can use to make your prompts better or how to chain multiple AI queries together. I will also discuss what are UX considerations when building AI tools and how to measure the impact of changes in AI systems... and try to answer the question - "should I integrate AI into my application?"

Bringing the Power of AI into your Editor with GitHub Copilot

GitHub Copilot is an AI pair programmer tool that puts the collective knowledge of millions of developers right at your fingertips, directly in your IDE.

During the talk, Krzysztof, a core team member behind GitHub Copilot, will demo how Copilot works and discuss the design principles used while creating the project.

He will also dive into some of the project's technical details - how Copilot communicates with its AI, what "queries" it uses, how it processes responses, and how it integrates with various IDE to create characteristic Copilot's UX.

LSP - magic behind your IDE

Language Server Protocol (LSP) is a project that has changed how editor tooling is built over the past two years. It is a specification of the communication between a client (editor) and a server that provides language tooling capabilities such as autocomplete, tooltips, etc. It reduces the m-times-n problem to the m-plus-n problem —similar to how Virtual Machines solve the same problem for deploying code to many platforms.

In the talk, I'll give general overview of the protocol, show some of its capabilities and explain why it is so important. I'll also dive into some sample implementations, showing you how you can leverage LSP to create rich editing experience for many different editors.

Behind F# editor tooling

F# editor tooling is in a unique position among FP languages - cross-platform, feature-rich, stable, innovative and supported and actively developed by both OSS community and commercial vendors. It's also ubiquitous - powered by the compiler which is developed with tooling in mind.

By the end of the talk, you should have an idea of how to design pieces of a compiler so that accurate tooling can be built, how constraints of a language affect tooling, and some of the challenges tooling developers face.

Reinventing MVC pattern for web programming with F#

The MVC pattern has been one of the most important architectural patterns for server-side web development - it has been implemented and popularized by frameworks like Ruby On Rail or ASP.NET MVC. However, this pattern was traditionally coupled with object-oriented programming. In the talk, I will show how to reinvent MVC pattern, and structure your web application in a functional language - F#.

The talk will cover some brief introduction to F# - modern functional programming language running on .Net platform, show how to model MVC layers using functional composition, and at the end show some examples of applying MVC pattern with Saturn - opinionated, web development framework for F# which implements the server-side, functional MVC pattern

Let's code together - bringing F# to JS world.

Javascript has conquered the software development world - developers can use it in the browser, on the server, to write mobile apps, on the desktop with Electron, and even to create serverless services. Whether you like the language or not, the truth is JS developers have built an incredible ecosystem with libraries and tools to do almost anything.

During the talk, I'll show how to bring the power of F# - robust, static type system with type inference, pattern matching, and immutable design, and succinct syntax - to this vast and rich JS world using Fable - F# to JS compiler.

It will be a practical talk, showing various use cases of Fable - from building React-based web applications, through building serverless, edge web services using Cloudflare Workers, creating mobile apps, to building VSCode extensions.

.NET Developer Conference '23 Sessionize Event

November 2023 Köln, Germany

DevConf 2023 Sessionize Event

November 2023 Łódź, Poland

Porto Tech Hub Conference 2023 Sessionize Event

October 2023 Porto, Portugal

meet.js Summit 2022

Bringing the Power of AI into your Editor with GitHub Copilot

September 2022 Poznań, Poland

JSNation 2022

Bringing the Power of AI into your Editor with GitHub Copilot

June 2022 Amsterdam, The Netherlands

.NET Conf: Focus on F#

A Tour of F# Editor Tooling

July 2021

NDC Oslo 2020 Sessionize Event

June 2020 Oslo, Norway

Lambda Days 2020

Behind F# editor tooling

February 2020 Kraków, Poland

Scale By The Bay 2019

Hacking F# in JS ecosystem

November 2019 San Francisco, California, United States


LSP: the magic behind your IDE

November 2019 Bristol, United Kingdom

F# Zurich User Group

Reinventing MVC pattern for web programming with F#

October 2019 Zürich, Switzerland

Workshop - SAFE Stack (focused on Fable & Elmish)

October 2019 Zürich, Switzerland

Open F# 2019

Keynote - Ionide. The OSS Story
SAFE Stack Dojo

September 2019 San Francisco, California, United States

Fable Conf 2019

Building F# Tooling

September 2019 Antwerpen, Belgium

Prage F# User Group

State of the union

April 2019 Prague, Czechia

F# eXchange 2019

Reinventing MVC pattern for Web Programming with F#

April 2019 London, United Kingdom


Hacking F# in JS ecosystem
Reinventing MVC pattern for web programming with F#
Panel: OSS and .Net

February 2019 Brussels, Belgium

Workshop - F# development with SAFE Stack

Workshop - F# development with SAFE Stack

November 2018 Vienna, Austria

FableConf 2018 + RemmidemmiConf 2018

Keynote - Future of F# web development

October 2018 Berlin, Germany

Open F# 2018

Web Programming with F# and SAFE Stack (workshop)
Reinventing MVC pattern for web programming with F#
Challenges of post-OSS world.

September 2018 San Francisco, California, United States

OSCon Portland 2018

Getting started with Fable - F# to JS compiler

July 2018 Portland, Oregon, United States

NDC Oslo 2018 Sessionize Event

June 2018

New Crafts Paris 2018

Challenges of post-OSS world

May 2018 Paris, France

flatMap(Oslo) 2018

Getting started with Fable - F# to JS compiler (workshop)

May 2018 Oslo, Norway

NYC F# User Group

Reinventing MVC pattern for web programming with F#

April 2018 New York City, New York, United States

Talk for Jet.com

Challenges of post-OSS world.

April 2018 Hoboken, New Jersey, United States

The Hanselminutes podcast

F# and the functional SAFE Stack with Krzysztof Cieślak

March 2018

Workshop - Introduction to F#

January 2018 Kaunas, Lithuania

CodeMotion Milan 2017

Hacking F# in JS ecosystem

November 2017 Milan, Italy

Remmidemmi Conf 2017

Path to happiness with OSS

November 2017 Berlin, Germany

FableConf 2017

Building editor tooling with Fable
Write your own VS Code extension - workshop

September 2017 Bordeaux, France

New Crafts Paris 2017

Hacking F# in JS ecosystem

May 2017 Paris, France

Get.Net Lodz 2017

Hacking F# in JS ecosystem

April 2017 Łódź, Poland

F# eXchange 2017

What's new in F# xplat tooling in 2017?

April 2017 London, United Kingdom

.Net Fringe 2016

Getting productive with F# Open Source tooling

July 2016 Portland, Oregon, United States

F# Technology Creators Workshop

Ionide - new features

May 2016 Cambridge, United Kingdom

F# eXchange 2016

Forge - F# CLI tooling

April 2016 London, United Kingdom

NDC London 2016

Ionide and state of F# open source environment

January 2016 London, United Kingdom

Krzysztof Cieślak

Developer Tools Researcher, OSS contributor, FP enthusiast

Łódź, Poland

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