DeepAI
Log In Sign Up

Effects Without Monads: Non-determinism – Back to the Meta Language

05/16/2019
by   Oleg Kiselyov, et al.
0

We reflect on programming with complicated effects, recalling an undeservingly forgotten alternative to monadic programming and checking to see how well it can actually work in modern functional languages. We adopt and argue the position of factoring an effectful program into a first-order effectful DSL with a rich, higher-order 'macro' system. Not all programs can be thus factored. Although the approach is not general-purpose, it does admit interesting programs. The effectful DSL is likewise rather problem-specific and lacks general-purpose monadic composition, or even functions. On the upside, it expresses the problem elegantly, is simple to implement and reason about, and lends itself to non-standard interpretations such as code generation (compilation) and abstract interpretation. A specialized DSL is liable to be frequently extended; the experience with the tagless-final style of DSL embedding shown that the DSL evolution can be made painless, with the maximum code reuse. We illustrate the argument on a simple but representative example of a rather complicated effect – non-determinism, including committed choice. Unexpectedly, it turns out we can write interesting non-deterministic programs in an ML-like language just as naturally and elegantly as in the functional-logic language Curry – and not only run them but also statically analyze, optimize and compile. The richness of the Meta Language does, in reality, compensate for the simplicity of the effectful DSL. The key idea goes back to the origins of ML as the Meta Language for the Edinburgh LCF theorem prover. Instead of using ML to build theorems, we now build (DSL) programs.

READ FULL TEXT

page 1

page 2

page 3

page 4

07/16/2018

In Praise of Impredicativity: A Contribution to the Formalisation of Meta-Programming

Processing programs as data is one of the successes of functional and lo...
12/30/2020

Analysis of MiniJava Programs via Translation to ML

MiniJava is a subset of the object-oriented programming language Java. S...
08/26/2017

The Unfolding Semantics of Functional Programs

The idea of using unfolding as a way of computing a program semantics ha...
11/05/2021

Pirouette: Higher-Order Typed Functional Choreographies

We present Pirouette, a language for typed higher-order functional chore...
08/28/2020

Practical Idiomatic Considerations for Checkable Meta-Logic in Experimental Functional Programming

Implementing a complex concept as an executable model in a strongly type...
08/20/2018

Fungi: Typed incremental computation with names

Incremental computations attempt to exploit input similarities over time...