Strachey Lecture: Bidirectional Computation is Effectful

A reconstruction (slides and voiceover) of a talk given at the Summit on Advances in Programming Languages (snapl.org/2015) in May 2015. Bidirectional transformations inherently involve state effects. Modelling them that way allows the incorporation of other effects too, such as I/O, non-determinism, and exceptions. We briefly outline the construction.