Tracing monadic computations and representing effects

TL;DR

This paper introduces monad transformers that enable automatic tracing of computations, revealing internal effects and observations, which enhances the functionality of monads, especially for non-terminating processes.

Contribution

It presents a novel approach to expose internal computation details by treating traces as results, expanding monad capabilities in functional programming.

Findings

Trace as result allows new functionalities in monads

Enhanced handling of non-terminating computations

Automatic accumulation of execution observations

Abstract

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.