Wed, Dec 12
Registration - 30 mins
Michael Snoyman - Applied Haskell Workshop
This full day workshop will focus on applying Haskell to normal, everyday programming. We'll be focusing on getting comfortable with common tasks, libraries, and paradigms, including:
- Understanding strictness, laziness, and evaluation
- Data structures
- Structuring applications
- Concurrency and mutability
- Library recommendations
By the end of the workshop, you should feel confident in working on production Haskell codebases. While we obviously cannot cover all topics in Haskell in one day, the goal is to empower attendees with sufficient knowledge to continue developing their Haskell skillset through writing real applications.
Attendees will be provided with a recommended prereading list to get the most out of the workshop.
Nikhil Barthwal - Embracing Functional Paradigm in F# for Enhanced Productivity
F# is a relatively new primarily Functional programming language for the .NET platform. It is a statically typed managed functional language that is fully inter-operable with other .NET languages like C#, Visual Basic.NET etc. It builds on the power of Functional Paradigm and combines it with .NET Object-Oriented model enabling the developer to use the best approach for a given problem.
This workshop introduces Functional Programming in F# from ground up. No prior experience in Functional Programming or .NET is needed, familiarity with a mainstream programming language like C++/Java/C# should be enough.
Functional programming (FP) offers several benefits. The code tends to be terse which leads to enhanced developer productivity. FP encourages pure functions which are much easier to reason about and debug, as well as eliminates large class of bugs due to side effect free programming. Moreover, immutability leads to easy parallelization of the code. Algebraic Data Types can be used to express domain object conveniently and control state space explosion.
F# is great practical choice for developing reliable and highly scalable real-world system that are quick and easy to develop due to the design of the language itself combined with the ability of the language to use a large no. of 3rd party libraries designed for the .NET platform.
Unfortunately, support for multiple paradigms often leads to confusion. Newcomers tend to find the transition from object-oriented world to functional world difficult. Moreover, it often leads to abuse where developer tries to use the same old imperative style of coding in a functional language and is unable to take advantage of the features, the language has to offer.
Anne Ogborn - Introduction to Logic Programming and SWI-Prolog
As machine learning matures, it is becoming obvious that we need explainable solutions. As functional programming
matures it becomes obvious that we need inference and nondeterminism. And linked open data demands reasoning.
This all day workshop will introduce the logic programming paradigm, in which programs are expressed as a set of
logical rules and executed by finding proofs of queries.
SWI-Prolog is the most highly developed and widely used language for logic programming.
The language, which has been in continuous use in academic research settings since it's invention in 1972, provides unparalleled power. Many problems which would be difficult to express in other languages are simple in SWI-Prolog.
SWI-Prolog is a 'batteries included' modern language, ready for real world tasks like web development and process control.
In this dynamic hands on workshop we'll learn the basics of SWI-Prolog, and look at some of the amazing things it can do.
Thu, Dec 13
Registration - 30 mins
Tony Morris / Aloïs Cochard - Introduction to Haskell syntax and tools
In this workshop, an attendee can expect to go from zero knowledge about Functional Programming in Haskell to familiarity with almost all of the syntax of the Haskell programming language, and associated tools. The general workflow of working with Haskell will be demonstrated in preparation for the subsequent workshops for the remainder of the day.
We will define Functional Programming to set the structure for the remainder of the day. We will explore most of the Haskell syntactic constructs and create your own reference material.
Participants will require a laptop with [GHC](http://haskell.org/ghc) and their favourite text editor installed.
We will explore the tooling that is provided with GHC to provide a basic workflow, so that the participant can later independently work with and explore other ideas with Haskell.
Erlang Bootcamp 1
FP on JVM Bootcamp 1
Brian McKenna - Starting Data61 Functional Programming Course
Following Tony and Alois' Introduction to Haskell syntax and tools, we will work through the first few modules of Data61's Functional Programming Course. These modules cover writing functions for the optional and list data types.
We will complete enough exercises to cover basic data types, functions and polymorphism. We'll practice the techniques of equational reasoning, parametricity and type/hole driven development. After completing these modules, you should be able to use the techniques to attempt most other exercises in the repository.
This workshop has the same requirements as Tony's introduction, along with a download of a recent version of the fp-course repository (https://github.com/data61/fp-course).
Lunch Break - 60 mins
Data61 Functional Programming Course...continued
Erlang Bootcamp 2
Debasish Ghosh - Power of Functions in a Typed World on the JVM
John Carmac once mentioned on twitter that "Sometimes, the elegant implementation is just a function. Not a method. Not a class. Not a framework. Just a function." In this talk we will discuss the power of functions in modeling real world applications on the JVM. When we say functions, we mean "pure" functions as in the world of mathematics.
Functions model behaviors, functions compose to build larger functions, and combined with a powerful type system allow us to abstract over the generalities in defining real world domain models. The combination of functions along with algebraic data types has proven to be extremely useful in designing large scale systems that are modular and extensible.
Scala is a typed functional (well, almost) language on the JVM. In this session we will discuss how the functional features of Scala offer many of the above benefits in designing large scale systems. If you are coming from an OO background, you will appreciate how an alternative approach to programming can make your systems simpler to design, implement and maintain.
Coffee/Tea Break - 30 mins
Mark Hibberd - Property Based Testing
Building on the earlier two introductions to functional programming with types, property based testing is the extra verification technique you need to ensure working software. We will work through the patterns of property based testing, starting with simple functions, working up to verification of a larger program.
By the end of this workshop participants will have a better understanding of the advantages of property based tests over example based tests, as well as acquiring the skills and confidence to start applying property based testing techniques to their current work.
This workshop has the same requirements as Tony's introduction, and will require a recent clone of the workshop repository available at https://github.com/markhibberd/property-based-testing-workshop.
Erlang Bootcamp 3
FP on JVM Bootcamp 3
Haskell Bootcamp Wrap up
Fri, Dec 14
Registration - 30 mins
Michael Snoyman - Functional Programming for the Long Haul
How do you decide whether a programming language is worth using or not? By necessity, such decisions are usually based on assessments that can be made relatively quickly: the ease of using the language, how productive you feel in the first week, and so on. Unfortunately, this tells us very little about the costs involved in continuing to maintain a project past that initial phase. And in reality, the vast majority of time spent on most projects is spent in those later phases.
I'm going to claim, based on my own experience and analysis of language features, that functional programming in general, and Haskell in particular, are well suited for improving this long tail of projects. We need languages and programming techniques that allow broad codebase refactorings, significant requirements changes, improving performance in hotspots of the code, and reduced debug time. I believe Haskell checks these boxes.
Welcome Address - 15 mins
Coffee/Tea Break - 15 mins
Tony Morris - Parametricity, Functional Programming, Types
In this talk, we define the principle of functional programming, then go into
detail about what becomes possible by following this principle. In particular,
parametricity (Wadler, 1989) and exploiting types in API design are an essential
property of productive software teams, especially teams composed of volunteers
as in open-source. This will be demonstrated.
Some of our most important programming tools are neglected, often argued away
under a false compromise. Why then, are functional programming and associated
consequences such as parametricity so casually disregarded? Are they truly so
unimportant? In this talk, these questions are answered thoroughly and without
We will define the principle of functional programming, then go into
detail about common problems to all of software development. We will build the
case from ground up and finish with detailed practical demonstration of a
solution to these problems. The audience should expect to walk away with a
principled understanding and vocabulary of why functional programming and
associated techniques have become necessary to software development.
Manoj Govindan - Going Forth to Erlang
Forth is a classic imperative stack-based programming language that fills a very specific niche. Erlang is a concurrent, functional, fault-tolerant programming language that occupies another, albeit wider, niche. There is very little in common between the two except for a shared respect for Alan Turing. This session is a case study that narrates the story of building a bridge between the two languages. The bridge allows for Forth nodes to run in a Erlang controlled world, with the ability to talk to Erlang nodes, send messages, invoke processes and so on.
In particular we'll discuss the various threading techniques used in Forth, listed below. We'll discuss how the choice of threading model impacts the design of the Erlang-Forth bridge.
Indirect Threaded Code (ITC)
A classical Forth threading technique. All the other threading schemes are considered "improvements" on this. Consider the following Forth expression:
: SQUARE DUP * ;
In a typical ITC Forth this would appear in memory as shown in the image below:
Direct Threaded Code (DTC)
This model is different from ITC in one respect: the Code Field contains actual machine code, rather than the address of some machine code.
Subroutine Threaded Code (STC)
This model relies on the following fact: a high-level Forth definition is nothing but a list of subroutines to be executed.
Token Threaded Code (TTC)
This model optimizes for size, at the cost of speed. A token-threaded Forth keeps a table of addresses of all Forth words. The token value is then used to index into this table, to find the Forth word corresponding to a given token.
Mark Hibberd - Hanging on in Quiet Desperation: Time & Programming
Time has a profound impact on the complexity of the systems we build.
A significant amount of this software complexity comes from either an inability to recall previous states or the inability to understand how a state was arrived at.
From the foundations of AI, LISP and functional programming , to causality in distributed systems , to the more grungy practices of immutable infrastructure, or the unreasonable effectiveness of fact-based approaches to large scale data systems; the ability to adequately cope with time, and the change and conflict it inevitably creates, is a common thread to being able to build and reason about these systems.
This talk looks at the impact of time on system design. We will walk through examples of large-scale systems and their battles with complexity. At the end of the talk, the audience should start to see the common spectre of time and have an appreciation of how understanding time is fundamental to maintaining clarity, correctness and reliability in systems.
 Situations, Actions, and Causal Laws
 Times, Clocks and the Ordering of Events in a Distributed System
Todd Sundsted / Michael Ho - Making the Switch: How We Transitioned from Java to Haskell
In this case study presentation, SumAll's CTO, Todd Sundsted, and Senior Software Engineer, Michael Ho, will discuss the move from Java to Haskell along two parallel paths. First, the business/political story — how SumAll convinced the decision makers, fought the nay-sayers, and generally managed the people impacted by the transition. Second, the technical story — how they actually replaced their Java code with Haskell code. Along the way, they will address their hopes and expectations from transitioning from Java to Haskell, and will conclude with the results they've gained and seen to date.
Anupam Jain - Purely Functional User Interfaces that Scale
A virtual cottage industry has sprung up around Purely functional UI development, with many available libraries that are essentially just variants on two distinct approaches: Functional Reactive Programming (FRP), and some form of functional views like "The Elm Architecture". After having worked extensively with each of them, I have found that none of the approaches scale with program complexity. Either they are too difficult for beginners trying to build a hello world app, or they have unpredictable complexity curves with some simple refactorings becoming unmanageably complex, or they "tackle" the scaling problem by restricting developers to a safe subset of FP which becomes painful for experienced developers who start hitting the complexity ceiling.
In this talk I give an overview of the current Purely Functional UI Development Landscape, and then present "Concur", a rather unusual UI framework, that I built to address the shortcomings of the existing approaches. In particular, it completely separates monoidal composition in "space" (i.e. on the UI screen), from composition in "time" (i.e. state transitions), which leads to several benefits. It's also a general purpose approach, with Haskell and Purescript implementations available currently, and can be used to build user interfaces for the web or for native platforms.
The biggest advantage of Concur that has emerged is its consistent UI development experience that scales linearly with program complexity. Simple things are easy, complex things are just as complex as the problem itself, no more. Reusing existing widgets, and refactoring existing code is easy and predictable. This means that Concur is suitable for all levels of experience.
- For Learners - Concur provides a consistent set of tools which can be combined in predictable ways to accomplish any level of functionality. Due to its extremely gentle learning curve, Concur is well suited for learners of functional programming (replacing console applications for learners).
- For experienced folks - Assuming you are already familiar with functional programming, Concur will provide a satisfying development experience. Concur does not artificially constrain you in any form. You are encouraged to use your FP bag of tricks in predictable ways, and you are never going against the grain. It's a library in spirit, rather than a framework.
Emily Pillmore - A Radically New Functional Blockchain Architecture: Chainweb
Proof-of-work blockchain networks like Bitcoin, Litecoin and Ethereum are characterized by low throughput (5-15 transactions per second). Efforts to improve throughput through protocol modifications, such as block size increases, have no hope of reaching levels required to take on modern fiat-currency payment networks. However, efforts that seek to replace Proof-of-Work (Proof-of-Stake and variants) or integrate it with off-chain networks and processes (payment channels, side chains) degrade assurance, censorship resistance or trustless-ness of the original design. Recovering and elaborating on early proposals for Bitcoin scaling, we present ChainWeb, a parallel-chain architecture which can combine hundreds to thousands of Proof-of-Work blockchains pushing throughput to 10,000 transactions per second and beyond. The network transacts a single currency, using atomic and trustless SPV (Simple Payment Verification) cross-chain transfers orchestrated at the application layer with capability and coroutine support in the Pact smart contract language. Chains incorporate each other’s Merkle tree receipts to enforce a single “super branch” offering an effective hash power that is the sum of each individual chain’s hash rate. In addition to massive throughput, other benefits accrue from having a truly parallelized smart-contract blockchain system.
Lunch Break - 60 mins
Aloïs Cochard - The Magnum Opus
From Ancient Egypt to the Middle Ages humanity lost it's way in the quest to find the philosopher's stone.
While following the recent advance in machine learning one might think that we are running in that same quest again,
only differences this time are that our philosopher's stone is deep learning and the promise is general artificial intelligence instead of immortality.
The current machine learning ecosystem is mainly based on python and pretty much feels like alchemy,
lot of trial and errors, lack of tooling and good engineering practices, ...
Let's take a tour of the current ecosystem and see how can we do better and safer high performance machine learning using Haskell!
Nikhil Barthwal - Implementing Event-Driven Microservices architecture in Functional language
Web services are typically stateless entities, that need to operate at scale at large. Functional paradigm can be used to model these web services work and offer several benefits like scalability, productivity, and correctness.
This talk describes how to implement Event-Driven Microservices with examples in F#. It starts with introducing Domain Driven Design to create Microservices boundaries. Using Discriminated Unions (F#'s Algebraic Data Types), the domain model can be captured as code eliminating the need for separate documentation. Moreover, using Computation expressions (F#'s Monads), one can model custom workflows easily.
It then introduces event-driven architecture, where every external action generates an event that the system responds to. Events act as the notification messages for any significant change in state and may generate other event(s) as services invoke each other. They are immutable by nature.
An explanation on why 2-phase commits cannot be used in Microservices having their own databases. Further the talk explains, how Event Driven Architecture solves this problem in an eventually consistent manner without sacrificing availability or partition tolerance. Distributed Sagas as a protocol for coordinating Microservices is introduced and its implementation in F# is also provided.
Event Sourcing can be used to model the system state. Event sourcing models the state of entity as a sequence of state-changing events. Whenever the state of a business entity changes, a new event is appended. List fold operation is ideal for implementing Event sourcing where the application reconstructs an entity's current state by replaying the events. An example with F#'s List.fold is provided.
Some aspects of evolutionary architecture are also discussed, particularly on how to evolve Microservices interface. F#'s Type providers can be used for the same though there are alternate approaches using Apache Thrift/Google Protobuf (They don't have support for F# but they do have support for C#, which F# code can leverage).
Events and their responses can be very easily modeled with Discriminated Unions. Data immutability captures the behavior of these events, since events are immutable by nature. A service can be thought of as a function that accepts an event (input) and gives back a response (output). A service may call other services, which is equivalent to a function calling other functions or even Higher-Order functions.
Immutability allows infinite scalability as it eliminated the need to worry about a mutex, a lock, or a race. As functional code is much more terse compares to object-oriented code, it provides productivity benefits. Its strict typing makes writing correct code easy as mismatch of types are caught at compile time.
Most of the services are implemented as set of pure functions. These functions which have no internal state, where outputs depend only on inputs and constants and it is very easy to test such functions. The absence of internal state means that there are no state transitions to test. The only testing left is to collect a bunch of inputs that tests for all the boundary conditions, pass each through the function under test and validate the output.
The objective of the talk is to show how to create a scalable & highly distributed web service in F#, and demonstrate how various characteristics of functional paradigm captures the behavior of such services architecture very naturally.
Experience Report 1
Zubin Duggal - The Future of Haskell Tooling
Haskell tooling, particularly editor and IDE integration has been sorely lacking for years. This talk will be a broad overview of the state of Haskell tooling, and the challenges faced by it. It will be derived from the experience of working on two summer of code projects trying to improve Haskell tooling.
For tooling users, we will discuss different Haskell tools available today(intero, haskell-ide-engine, ghcid etc.), their differences and trade-offs with respect to build tool support(stack, cabal, new-build, nix, make etc.), editor integration, features, limitations and speed.
We will go over the approach taken by haskell-ide-engine and the Language Server Protocol in order to solve these problems. Then we will discuss the new .hie file format designed to make information about Haskell source collected by GHC more accessible to tooling and users.
Finally, for budding tooling writers, we will discuss the various approaches to writing programs that extract information from and manipulate Haskell source, and their pros and cons:
- The GHC API
- Via ghc-mod and haskell-ide-engine
- GHC source plugins
- .hie files
- The GHC API
Experience Report 2
Coffee/Tea Break - 30 mins
George Wilson - Laws!
Laws, laws, laws. It seems as though whenever we learn about a new abstraction in functional programming, we hear about its associated laws. Laws come up when we learn about type classes like Functors, Monoids, Monads, and more! Usually laws are mentioned and swiftly brushed past as we move on to examples and applications of whatever structure we're learning about. But not today.
In this talk, we'll learn about Functors and Monoids, paying close attention to their laws. Why should our abstractions have laws? We'll answer this question both by seeing powers we gain by having laws, and by seeing tragedies that can befall us without laws.
Neeraj Sharma - BeamParticle - A Polyglot Dynamic Programming Engine
BeamParticle is an open source project built on top of the Erlang virtual machine (BEAM), which allows dynamic (re)programming in multiple programming languages. This project tries to take some simple decisions thereby making the life of developer easy in realizing dynamic code patching and reprogrammability. It is very easy to setup this software on any of the modern GNU/Linux distributions, although Debian packages are available for Ubuntu Xenial. The project supports six different programming languages; namely: Erlang, Elixir, Java, Python, Efene, and PHP.
The system is deployed in a limited capacity in production within redBus to serve numerous use cases.
Tanmai Gopal - Using Haskell to build a performant GraphQL to SQL compiler
- Motivation/Problem statement: Lifecycle of a GraphQL query
- Design Goals
- Why Haskell
- Compiler implementation details:
- Fast GraphQL parsing with parser combinators
- Modelling and manipulating the GraphQL AST with algebraic data types
- Software Transactional Memory: Concurrency constructs for scaling GraphQL subscriptions
- Summary with performance benchmarks
Dhaval Dalal / Ravindra Jaju - Code Jugalbandi - Exploring Concurrency
In Indian classical music, we have Jugalbandi, where two lead musicians or vocalist engage in a playful competition. There is jugalbandi between Flutist and a Percussionist (say using Tabla as the instrument). Compositions rendered by flutist will be heard by the percussionist and will replay the same notes, but now on Tabla and vice-versa is also possible.
In a similar way, we will perform Code Jugalbandi (http://codejugalbandi.org) to see how the solution looks using different programming languages. This time the focus of Code Jugalbandi will be on exploring concurrency models in different languages. Functional Programming has made programming concurrency easier as compared to imperative programming. For deeper perspective on Code Jugalbandi, check out http://codejugalbandi.org/#essence-of-code-jugalbandi
Saurabh Nanda - "Refresh-driven" development with Haskell & Elm
We sorely missed the rapid "refresh-based" feedback loop available in Rails (and other dynamically typed web frameworks), while writing Haskell. Change your code, hit save, and refresh your browser!
In this talk we will share a few tips on how we finally hit productivity nirvana with ghcid and automated code-gen.
Best of both worlds -- rock-solid type-safety AND being able to reload code with every change.
Luka Jacobowitz - Testing in the world of Functional Programming
Testing is one of the most fundamental aspects of being a software developer. There are several movements and communities based on different methodologies with regards to testing such as TDD, BDD or design by contract. However, in the FP community testing is often not a large topic and is often glossed over. While it’s true that testing in functional programming tends to be less important, there should still be more resources on how to create tests that add actual value.
This talks aims to provide exactly that, with good examples on how to leverage property based testing, refinement types and the most difficult part: figuring out how to test code that interacts with the outside world.
BoF - 60 mins
Networking Dinner - 120 mins
Sat, Dec 15
Registration - 30 mins
Day 2 - Opening Keynote - 45 mins
Important Announcements - 15 mins
Coffee/Tea Break - 15 mins
Ravi Mohan - Experience Report: Building Shin - A Typed Functional Compiler For Computational Linear Algebra Problems.
Abstract: I wrote a distributed (mostly) Functional Compiler in Scheme, OCaml and Elixir that incorporates knowledge of Computational Linear Algebra and domain specific knowledge to generate highly optimized linear algebra code from specification of problems. This talk is about lessons learned in the process.
In every domain that uses computational linear algebra (which is all of engineering and science), we encounter the 'how to optimize a linear algebra expression into an optimized sequence of BLAS (or LAPACK or $linear_algera library) kernel calls' problem.
Example: (if the math equations make you want to tear your hair out and go jump off a cliff, don't worry, it is just an example, you don't have to grok it. Just skim the equations The basic problem being addressed here is that solving such equations with code takes up a lot of effort and time from experts in computational linear algebra)
Here is a linear algebra expression from a genetics problem , specifically GWAS -Genome Wide Association Studies, looking for significant associations for millions of genetic markers- where the essence of the problem  comes down to generating the most efficient algorithm possible that solves these equations
This in turn involves solving a 2 dimensional sequence of Generalized Least Squared Problems of the form
The algorithms to solve these can be directly coded up in Matlab or Julia. But there are problems with this approach, with this specific problem.
1. For different input sizes, different algorithms give the most optimal performance. Which algorithm do you code up?
2. Even for a given input size, there are multiple algorithms that compute the same result, but have differing computational characteristics depending on the hardware etc. How do you generate the optimal algorithm for your hardware ?
3. Most importantly the structure of *this* specific problem allows optimizations that are specific to the problem which are not built into generic linear algebra routines. (Obviously, one can't expect MATLAB to incorporate problem specific information for every scientific/engineering problem ever). The GLS problems are connected to others, thus saving intermediate results can save hours of computation vs calculating every GLS problem from scratch
In practice, one needs to be an expert in Computational Linear Algebra to come up with the optimized algorithm for a domain specific problem, and then write (say Fortran) code to use BLAS, LAPACK etc optimally to actualize this algorithm, often with much iteration, often consuming 100s of hours.
Incorporating this 'expert knowledge' into a compiler speeds up the time taken to arrive at the best solution (often by a factor of 100 or 1000), and allows Computational Linear Algebra experts to do more interesting things, like focus on their research.
For this particular problem, the above equations, and additional knowledge of the problem domain are the input into an expression compiler. The output is highly efficient and 'proved correct' code
In compiler terms, incorporating domain knowldege into the compilation process results in being able to apply optimizations to the generated Syntax Trees/Graphs, resulting in optimal algorithms. (note: the output of the compiler is a program in another language- say Matlab).
In essence, "Domain Specific Compilers" consume knowledge about the structure of a problem and generate optimized code that solves that problem.
Shin is one such compiler. It consumes a problem description and outputs highly efficient Julia code that solves the problem.
This talk focuses on the engineering challenges I faced in building this compiler, with a special focus on the approaches that failed 
"Shin" is the Hebrew letter, not the English word meaning 'front of the leg between knee and ankle' ;-).
Every company uses names from a common theme to name their servers and components - Athena, Zeus, Hercules , or Thor, Loki, Odin, or Jedi, Sith, Skywalker etc. We use Hebrew words, so we have Ruach, Melekh, Malkuth etc..
Emily Pillmore / Stuart Popejoy - Pact: An Open Source Language for Smart Contracts
In this talk we'll discuss the design and implementation of a smart contract property verification tool for Pact.
The revolutionary idea of putting computer programs in a blockchain to create smart contracts has opened up a whole new world of possibilities. But these programs have very different characteristics from other software. This talk explores these differences, some of the challenges that have been encountered, and then discusses how Kadena is solving these problems with its smart contract language Pact. We'll discuss the design and implementation of a smart contract property verification tool for Pact. We leverage these (lack of) features to build a system capable of proving many properties of contracts via the Z3 SMT solver. We'll also give examples of real bugs caught by the system.
Aaron W Hsu - Does APL Need a Type System?
APL is known for its concise problem-solving expressiveness, and it is used very successfully in places where high-quality and rapid iteration are requirements, not luxuries. Static Type Systems have had tremendous success throughout the computing industry, even receiving positive HCI usability studies that demonstrate their effectiveness on a number of metrics with mainstream and functionally-oriented programming languages. This success leads many programmers to take the value of type systems as a given, especially as mission-criticality and the age of a project increase. Therefore, it comes as a surprise to many, when learning about APL, that it has spent so long as an untyped, interpreted language in domains and use cases where traditional wisdom would suggest the need for a typed, compiled language.
But APL is not like other languages, and its unique features and historical uses warrant a careful revisiting of the question of type systems. In this talk we will explore whether or not APL needs a type system, whether it would benefit from having one, what that might look like, and how the interaction between APL and type theory might inform the design and use of type systems in general.
Harendra Kumar - High Performance Haskell
Haskell can and does perform as well as C, sometimes even better. However,
writing high performance software in Haskell is often challenging especially
because performance is sensitive to strictness, inlining and specialization.
This talk focuses on how to write high performance code using Haskell. It is
derived from practical experience writing high performance Haskell libraries. We
will go over some of the experiences from optimizing the "unicode-transforms"
library whose performance rivals the best C library for unicode normalization.
From more recent past, we will go over some learnings from optimizing and
benchmarking "streamly", a high performance concurrent streaming library. We
will discuss systematic approach towards performances improvement, pitfalls and
the tools of the trade.
Lunch Break - 60 mins
Debasish Ghosh - Managing Effects in Domain Models - The Algebraic Way
When we talk about domain models, we talk about entities that interact with each other to accomplish specific domain functionalities. We can model these behaviors using pure functions. Pure functions compose to build larger behaviors out of smaller ones. But unfortunately the real world is not so pure. We need to manage exceptions that may occur as part of the interactions, we may need to write stuff to the underlying repository (that may again fail), we may need to log audit trails and there can be many other instances where the domain behavior does not guarantee any purity whatsoever. The substitution model of functional programming fails under these conditions, which we call side-effects.
In this session we talk about how to manage such impure scenarios using the power of algebraic effects. We will see how we can achieve function composition even in the presence of effects and keep our model pure and referentially transparent. We will use Scala as the implementation language.
In discussing effects we will look at some patterns that will ensure a clean separation between the algebra of our interface and the implementation. This has the advantage that we can compose algebras incrementally to build richer functionalities without committing to specific implementations. This is the tagless final approach that offers modularity and extensibility in designing pure and effectful domain models.
Srihari Sriraman - Generative Testing Patterns
Tests are good. Generative tests are better. But we don't write them often enough. Why not?
Generative testing isn't new; John Hughes' QuickCheck is now implemented in 30 languages. Yet, it is still not an every day tool for most software teams. Why not?
I have seen that maintaining a generative, or simulation testing suite can require the full-time attention of a few senior engineers. And over time, the tests become complex, brittle, ineffective, and hard to diagnose.
But isn't generative testing supposed to make testing simpler, and more effective?
I believe that it requires a rather different paradigm of thought from what we're used to with traditional testing. And recognising this paradigm shift can help us leverage it effectively.
I'll discuss a holistic perspective of generative testing to elucidate this thought paradigm.
Using a practical scenario, I'll discuss the patterns that emerge from this thinking, and how they address the concerns of making generative tests more effective, and maintainable.
Experience Report 3
Experience Report 4
Coffee/Tea Break - 15 mins
Anne Ogborn - let over logic - What functional programming can learn from logic programming
48 years after it's invention, logic programming remains a less frequently used paradigm.
What can functional programming learn from logic programming?
Unification and nondeterminism are powerful constructs not strictly relegated to logic programming. We'll look at unification, nondeterministic completion, probabilistic computation, and constraint propagation in functional contexts.
Aaron W Hsu / Dhaval Dalal / Morten Kromberg - Array-oriented Functional Programming
APL is the original functional programming language, the grand-daddy, the Godfather, and the old workhorse. But don't let Grandpa's age fool you. APL programmers have been leveraging the use of functional programming with arrays long before it was cool to be chasing pointers in an ADT using statically typed pattern matching, and they've refined their own style and approach to getting the most from a "functional paradigm."
In this workshop, you will have the chance to spend some time thinking like a functional array programmer. What makes it different? How does the code look at the end? What thought process do you go through to get there? Get a chance to play around with some classic problems and try solving them "the APL way."
Taijiquan Classics say, "Four ounces deflects a thousand pounds."
APLers might say instead, "Fifty characters solve a thousand problems."
Markus Hauck - Free All The Things!
Have you ever asked yourself why we only free monads? Turns out there are a lot of other structures that want to be liberated from the constraints of their existence! In this talk, we will investigate what other poor (algebraic) structures we can free from the dirty hands of imperative programmers. Our journey starts with the well-known free monads, but after that we will have a look at all the other interesting structures that can be freed and of course we will also look at what we can do with them.
Closing Talk - 45 mins
Sun, Dec 16
Registration - 30 mins
Tony Morris - Let's Lens
Let's Lens presents a series of exercises, in a similar format to the Data61 functional programming course material. The subject of the exercises is around the concept of lenses, initially proposed by Foster et al., to solve the view-update problem of relational databases.
The theories around lenses have been advanced significantly in recent years, resulting in a library, implemented in Haskell, called lens.
This workshop will take you through the basic definition of the lens data structure and its related structures such as traversals and prisms. Following this we implement some of the low-level lens library, then go on to discuss and solve a practical problem that uses all of these structures.
Ravindra Jaju / Aditya Athalye / Dhaval Dalal - The Clojuring: (hit rubber road)
distance(clojure-code, production)→ 0
Clojure is capable of leveraging everything your JVM provides. And you are convinced of the benefits this LISP brings to your productivity. In this workshop, we target bridging the gap between your expressive and beautiful Clojure code, and the huge, daunting world of the Enterprise. With some small, helpful steps.
We'll specifically target
- Going beyond the linear flows - making core.async practical
- Confidence building measures - Clojure spec
- Demystifying the wormhole - JVM interop
- Practical tidbits - Introducing Clojure to your existing apps
- Graduating - Build tooling and publishing for both library and standalone application use-cases
Aaron W Hsu / Morten Kromberg - APL Workshop Intensive