POPL 2017
Sun 15 - Sat 21 January 2017
Thu 19 Jan 2017 14:45 - 15:10 at Auditorium - Functional Programming with Effects Chair(s): Kathleen Fisher

We explore the design and implementation of Frank, a strict functional programming language with a bidirectional effect type system designed from the ground up around a novel variant of Plotkin and Pretnar’s effect handler abstraction.

Effect handlers provide an abstraction for modular effectful programming: a handler acts as an interpreter for a collection of commands whose interfaces are statically tracked by the type system. However, Frank eliminates the need for an additional effect handling construct by generalising the basic mechanism of functional abstraction itself. A function is the special case of a Frank operator that interprets no commands.

Moreover, Frank’s operators can be multihandlers which simultaneously interpret commands from several sources at once, without disturbing the direct style of functional programming with values.

Effect typing in Frank employs a novel form of effect polymorphism which avoids all mention of effect variables in source code. This is achieved by propagating an ambient ability inwards, rather than accumulating unions of potential effects outwards.

We introduce Frank by example, and then give a formal account of the Frank type system and its semantics. We introduce Core Frank by elaborating Frank multihandlers into functions, case expressions, and unary handlers, and then give a sound small-step operational semantics for Core Frank.

Programming with effects and handlers is in its infancy. We contribute an exploration of future possibilities, particularly in combination with other forms of rich type system.

Thu 19 Jan
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14:20 - 16:00: Functional Programming with EffectsPOPL at Auditorium
Chair(s): Kathleen FisherTufts University
14:20 - 14:45
Daan LeijenMicrosoft Research
14:45 - 15:10
Sam LindleyUniversity of Edinburgh, Conor McBride, Craig McLaughlinThe University of Edinburgh
15:10 - 15:35
Danel AhmanUniversity of Edinburgh, Cătălin HriţcuInria Paris, Kenji MaillardInria Paris, ENS Paris, and Microsoft Research, Guido MartínezCIFASIS-CONICET, Argentina, Gordon Plotkin, Jonathan ProtzenkoMicrosoft Research, Aseem RastogiMicrosoft Research India, Nikhil SwamyMicrosoft Research
15:35 - 16:00