OCaml Stepper

April 3, 2025

News

(2025 March 29) Created this page

What is the OCaml Stepper?

The OCaml Stepper is an algebraic stepper (as pioneered in the Racket language) that shows how a program is executed step by step. It is implemented in Ochanomizu University and is used in the functional programming course. It supports most of the basic language constructs, including conditionals, recursive functions, datatype declarations and pattern matching, exception handling, I/O, references, and modules, but it does not support advanced features such as imperative features, objects, functors, GADTs, and algebraic effects. The OCaml Stepper runs from Visual Studio Code.

Demo

Installation

For OCaml 4.14.2:

opam pin add stepper http://pllab.is.ocha.ac.jp/~asai/Stepper/4.14.2/stepper.tar.gz

For OCaml 4.12.0 (not maintained anymore):

opam pin add stepper http://pllab.is.ocha.ac.jp/~asai/Stepper/4.12.0/stepper.tar.gz

Using the OCaml Stepper in Visual Studio Code

Install the extension ocha-platform by downloading vsix file from the latest release and then executing

code --install-extension ocha-platform-?.?.?.vsix

or through the ``Install from VSIX'' command in the Extensions view command dropdown.

Button Usage

Start: start the OCaml Stepper
Prev: go to the previos step
Next: go to the next step
Skip: evaluate the current expression completely (without showing the steps) and skip to the result
Forward: go to the next toplevel definition (such as the next test case)
End: end the OCaml Stepper

Papers

Asai, K., and H. Akiyama ``Algebraic Stepper for Simple Modules,'' ACM SIGPLAN Workshop on Partial Evaluation and Program Manipulation (PEPM '25), pp. 13-29 (January 2025).
Furukawa, T., Y. Cong, and K. Asai ``Stepping OCaml,'' Trends in Functional Programming in Education (June 2018). Post proceedings version in Electronic Proceedings in Theoretical Computer Science 295, pp. 17-34 (June 2019).
Cong, Y., and K. Asai ``Implementing a stepper using delimited continuations,'' In J. H. Davenport and F. Ghourabi editors, 7th International Symposium on Symbolic Computation in Software Science (SCSS '16), EPiC Series in Computing, Vol. 39, pp. 42-54 (March 2016).

Members

Hinano Akiyama
Tsukino Furukawa
Youyou Cong
Kenichi Asai

This document was translated from L^AT_EX by H^EV^EA.