[Pl-seminar] 5/11 Seminar: Gabriel Scherer, New language ideas for user-defined side-effects: algebraic effect handlers

[William J. Bowman]

NUPRL Seminar presents

Gabriel Scherer
Northeastern University

11:45--13:25
Wednesday May 11, 2016
Room 366 WVH (http://www.ccs.neu.edu/home/wand/directions.html)
Host: Gabriel Scherer


New language ideas for user-defined side-effects: algebraic effect handlers

Abstract:
This talk reports on some cool ideas I learned during a week-long
seminar in Dagstuhl last month; it will present other people's work,
not my own. It is aimed at an audience interested in programming
language design in general, but not familiar with the theoretical
treatment of pure languages and side-effects.

We shall start with *demos* first, explaining short code examples in
three programming languages: ML with exceptions as a warmup, then the
new language 'Eff' of Matija Pretnar and Andrej Bauer, that first
implemented so-called effect handlers, and finally the language
'Frank' of Conor McBride, that integrates these handlers in a more
uniform style of "effectful call-by-value programming".

Only second will we discuss some *theory*, in an accessible way:
monads and algebraic effects, which are two distinct ways to formalize
side-effects, and the difference between "direct" and "indirect" style
of effectful programming.

Underlying this talk are two larger, important questions of
programming language design, that will be touched during the talk and
we can discuss further afterwards:
- Do programming language need a facility for user-defined side-effects?
- When should we encode new design ideas as libraries/macros in an
  expressive language, and when should we design languages afresh for
  them?


Bio:
Gabriel is interested in theoretical aspects of type systems,
programming language implementation, general programming language
concepts, and even some syntactic aspects. He has a preference for the
formalizable aspects, or formalizable approaches to programming
language aspects, rather than the often subjective appeal to taste or
intuition.

-- 
William J. Bowman
Northeastern University
College of Computer and Information Science
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