ML Family Workshop, September 2017

Thursday September 7, 2017, Oxford, UK
(co-located with ICFP 2017)

ML is a family of programming languages that includes Standard ML, OCaml, F#, Alice ML, Dependent ML, Flow Caml, JoCaml, Manticore, MetaOCaml, SML#, and many others. All ML languages share several fundamental traits, besides a good deal of syntax. They are higher-order, strict, mostly pure, and typed, with algebraic and other data types. Their type systems are derived from Hindley-Milner. The development of these languages has inspired a significant body of computer science research and influenced the design of many other programming languages, including Haskell, Rust, and Scala.

ML workshops have been held in affiliation with ICFP continuously since 2005. This workshop specifically aims to recognise the entire extended ML family and to provide a forum for presenting and discussing common issues, both practical (compilation techniques, implementations of concurrency and parallelism, programming for the Web) and theoretical (fancy types, module systems, metaprogramming). The scope of the workshop includes all aspects of the design, semantics, theory, application, implementation, and teaching of the members of the ML family. We also encourage presentations from related languages (such as ATS, Eff, F*, Koka, Links, Rust, Scala, Swift, etc.), to exchange experience of further developing ML ideas. Last year's ML Family workshop included talks covering eight different ML dialects and related languages: Eff, F#, F*, Links, Manticore, OCaml, SML, and SML#.

The ML family workshop will be held in close coordination with the OCaml Users and Developers Workshop.

Accepted talks

  • Effects without monads: non-determinism. Oleg Kiselyov.
  • Tierless modules. Gabriel Radanne and Jérôme Vouillon.
  • Efficient representation of large, dynamic sequences in ML. Arthur Chargueraud and Mike Rainey.
  • Mergeable types. Gowtham Kaki, KC Sivaramakrishnan, Samodya Abeysiriwardane, and Suresh Jagannathan.
  • Towards abductive functional programming. Koko Muroya.
  • Typer: an infix statically typed Lisp. Pierre Delaunay, Vincent Archambault-Bouffard, and Stefan Monnier.
  • Making SML# a general-purpose high-performance language. Atsushi Ohori, Kenjiro Taura, and Katsuhiro Ueno.
  • First-class subtypes. Jeremy Yallop and Stephen Dolan.
  • Effectively tackling the awkward squad. Stephen Dolan, Spiros Eliopoulos, Daniel Hillerström, Anil Madhavapeddy, KC Sivaramakrishnan, and Leo White.
  • Relational conversion for OCaml. Petr Lozov and Dmitry Boulytchev.
  • VOCAL -- A Verified OCAml Library. Arthur Charguéraud, Jean-Christophe Filliâtre, Mário Pereira, and François Pottier.


9:00--9:05 Welcome

9:05--10:00 Invited Talk
State machines all the way down
          Edwin Brady

A useful pattern in dependently typed programming is to define a state
transition system, for example the states and operations in a network
protocol, as an indexed monad. We index each operation by its input and
output states, thus guaranteeing that operations satisfy pre- and
post-conditions, by typechecking. However, what if we want to write a
program using several systems at once? What if we want to define a high
level state transition system, such as a network application protocol,
in terms of lower level states, such as network sockets and mutable

In this talk, I will present an architecture for dependently typed
applications based on a hierarchy of state transition systems,
implemented in a generic data type ST. This is based on a monad indexed
by contexts of resources, allowing us to reason about multiple state
transition systems in the type of a function. Using ST, we show: how to
implement a state transition system as a dependent type, with type level
guarantees on its operations; how to account for operations which could
fail; how to combine state transition systems into a larger system; and,
how to implement larger systems as a hierarchy of state transition
systems. I will illustrate the system with a high level network
application protocol, implemented in terms of POSIX network sockets.

10:00--10:30 Break

10:30--11:45 Types and modules
Mergeable types (pdf)
Gowtham Kaki, KC Sivaramakrishnan, Samodya Abeysiriwardane, and Suresh Jagannathan
Tierless modules (pdf)
Gabriel Radanne and Jérôme Vouillon
First-class subtypes (pdf)
Jeremy Yallop and Stephen Dolan
11:45--12:00 Break

12:00--12:25 Verification
VOCAL -- A Verified OCAml Library (pdf)
Arthur Charguéraud, Jean-Christophe Filliâtre, Mário Pereira, François Pottier

12:25--14:00 Lunch

14:00--15:15 Programming language design
Typer: an infix statically typed Lisp (pdf)
Pierre Delaunay, Vincent Archambault-Bouffard, and Stefan Monnier
Relational conversion for OCaml (pdf )
Petr Lozov and Dmitry Boulytchev
Towards abductive functional programming (pdf)
Koko Muroya

15:15--15:30 Break

15:30--16:20 Performance
Making SML# a general-purpose high-performance language (pdf)
Atsushi Ohori, Kenjiro Taura, and Katsuhiro Ueno
Efficient representation of large, dynamic sequences in ML (pdf)
Arthur Chargueraud and Mike Rainey

16:20--16:50 Break

16:50--17:40 Effects
Effects without monads: non-determinism (pdf)
Oleg Kiselyov
Effectively tackling the awkward squad (pdf)
Stephen Dolan, Spiros Eliopoulos, Daniel Hillerström, Anil Madhavapeddy, KC Sivaramakrishnan, and Leo White


We acknowledge the whole breadth of the ML family and aim to include languages that are closely related, such as Rust and Scala. Those languages have implemented and investigated run-time and type system choices that may be worth considering for OCaml, F# and other ML languages. We also hope that the exposure to state of the art ML might favourably influence those related languages. Specifically, we seek research presentations on topics including (but not limited to):

  • Language design: abstraction, higher forms of polymorphism, concurrency, distribution and mobility, staging, extensions for semi-structured data, generic programming, object systems, etc.
  • Implementation: compilers, interpreters, type checkers, partial evaluators, runtime systems, garbage collectors, foreign function interfaces, etc.
  • Type systems: inference, effects, modules, contracts, specifications and assertions, dynamic typing, error reporting, etc.
  • Applications: case studies, experience reports, pearls, etc.
  • Environments: libraries, tools, editors, debuggers, cross-language interoperability, functional data structures, etc.
  • Semantics: operational and denotational semantics, program equivalence, parametricity, mechanization, etc.

Four kinds of submissions will be accepted: Research Presentations, Experience Reports, Demos and Informed Positions.

  • Research Presentations: Research presentations should describe new ideas, experimental results, or significant advances in ML-related projects. We especially encourage presentations that describe work in progress, that outline a future research agenda, or that encourage lively discussion. These presentations should be structured in a way which can be, at least in part, of interest to (advanced) users.
  • Experience Reports: Users are invited to submit Experience Reports about their use of ML and related languages. These presentations do not need to contain original research but they should tell an interesting story to researchers or other advanced users, such as an innovative or unexpected use of advanced features or a description of the challenges they are facing or attempting to solve.
  • Demos: Live demonstrations or short tutorials should show new developments, interesting prototypes, or work in progress, in the form of tools, libraries, or applications built on or related to ML and related languages. (You will need to provide all the hardware and software required for your demo; the workshop organisers are only able to provide a projector.)
  • Informed Positions: A justified argument for or against a language feature. The argument must be substantiated, either theoretically (e.g. by a demonstration of (un)soundness, an inference algorithm, a complexity analysis), empirically or by substantial experience. Personal experience is accepted as justification so long as it is extensive and illustrated with concrete examples.


The ML 2017 workshop will continue the informal approach followed since 2010. Presentations are selected from submitted abstracts. There are no published proceedings, so contributions may be submitted for publication elsewhere. We hope that this format will encourage the presentation of exciting (if unpolished) research and deliver a lively workshop atmosphere.

Each presentation should take 20-25 minutes, except demos, which should take 10-15 minutes. The exact time will be decided based on the number of accepted submissions. The presentations will likely be recorded.


ML 2017 is an informal workshop without proceedings. We are planning to publish a post-proceedings and to invite interested authors of selected presentations to expand their abstracts for inclusion.

Coordination with the OCaml Users and Developers Workshop

The OCaml workshop is seen as more practical and is dedicated in significant part to OCaml community building and the development of the OCaml system. In contrast, the ML family workshop is not focused on any language in particular, is more research-oriented, and deals with general issues of ML-style programming and type systems. Yet there is an overlap, which we are keen to explore in various ways. The authors who feel their submission fits both workshops are encouraged to mention it at submission time or contact the programme chairs.

Submission details

Submissions should be at most two pages, in PDF format, and printable on US Letter or A4 sized paper. A submission should have a synopsis (2--3 lines) and a body between 1 and 2 pages, in one- or two-column layout. The synopsis should be suitable for inclusion in the workshop programme. The bibliography will not be counted against the page limit.

Submissions must be uploaded to the workshop submission website

before the submission deadline (Wednesday 31st May). If you have a question concerning the scope of the workshop or the submission process, please contact the programme chair.

Important dates

Wednesday 31st May (any time zone)Abstract submission deadline
Wednesday 28th JuneAuthor notification
Thursday 7th September 2017ML Family Workshop

Programme committee