Tracing monadic computations and representing effects

Maciej Piróg
(Department of Computer Science, University of Oxford)
Jeremy Gibbons
(Department of Computer Science, University of Oxford)

In functional programming, monads are supposed to encapsulate computations, effectfully producing the final result, but keeping to themselves the means of acquiring it. For various reasons, we sometimes want to reveal the internals of a computation. To make that possible, in this paper we introduce monad transformers that add the ability to automatically accumulate observations about the course of execution as an effect. We discover that if we treat the resulting trace as the actual result of the computation, we can find new functionality in existing monads, notably when working with non-terminating computations.

In James Chapman and Paul Blain Levy: Proceedings Fourth Workshop on Mathematically Structured Functional Programming (MSFP 2012), Tallinn, Estonia, 25 March 2012, Electronic Proceedings in Theoretical Computer Science 76, pp. 90–111.
Published: 11th February 2012.

ArXived at: http://dx.doi.org/10.4204/EPTCS.76.8 bibtex PDF
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