A Guided Tour Through Oxidized Caml

This will be held at ICFP/SPLASH 2025, with inputs variously from Anil Madhavapeddy, KC Sivaramkrishnan, Richard Eisenberg, Chris Casinghino, Gavin Gray, Will Crichton, Shriram Krishnamurthi, Patrick Ferris.

URL: https://conf.researchr.org/track/icfp-splash-2025/icfp-splash-2025-tutorials Status: WIP, unreleased

We have two 90 minute chunks, first at 1400-1530 and then 1600-1730.

Getting started

Use the pre-built Docker Hub image.

1. Open this folder in VS Code
2. Click "Reopen in Container" when prompted
   • OR: Cmd/Ctrl + Shift + P → "Dev Containers: Reopen in Container"

The docker image has three switches installed

opam@d573f5771225:/workspaces/oxcaml-icfp-tutorial$ opam switch
#  switch      compiler                                          description
→  5.2.0+ox    ocaml-variants.5.2.0+ox                           5.2.0+ox
   5.3         ocaml-base-compiler.5.3.0                         5.3
   5.3.0+tsan  ocaml-option-tsan.1,ocaml-variants.5.3.0+options  5.3.0+tsan

First Session

Activity 1 (15m)

What: A pretest containing 4-5 OCaml programs in which we ask participants questions about memory allocation, thread safety, etc.

Why: We propose this activity for two reasons:

• We want to understand the OCaml conceptual model participants have coming into the tutorial. For example, a “portable function” may not mean much to the participant that doesn’t have a proper conceptual model of thread safety.
• If we reuse the same code snippets in the slides portion, then participants are already familiar with the code and only need to focus on the OxCaml concepts. By forcing participants to wrestle with the code and concepts beforehand, they are more likely to engage with and better understand the material.

Conceptual Model (60m)

• What: This is the slides portion of the tutorial where y’all get to teach the different concepts of OxCaml. This should leave participants with an understanding of: the difference between a mode and modality, past and future axes, what each axis does, etc.
• Why: This is our chance to provide the OxCaml conceptual model and provide answers to the pretest questions, allowing participants to self-correct their model.

Activity 2 (15m)

• What: A collection of questions regarding the conceptual model of OxCaml.
• Why: We want to test participants on the conceptual model of OxCaml to see how effective the lecture portion of the tutorial was with an eye towards improving these materials for the future. We also want to see what concepts are difficult (e.g., do a majority of participants misunderstand modalities?).

Break (30m)

Second Session

Hands-on Activity (60m)

What: We provide a set of OCaml programs and ask participants to translate them to OxCaml. (e.g., x parameter should be local, now fix all the errors!) They would do this in the online instance and we can gather telemetry data about the state of their programs and the type errors they get.

Why: It’s one thing to learn about OxCaml, but it’s another to use it. Participants should leave the tutorial with some degree of certainty that they could use OxCaml in their own code. Participants will get the opportunity to try it out "in the wild" and get their questions answered from experts (that doesn’t happen often). We also get a sense of how the conceptual model, as taught, translates to programmers code. With telemetry data we can see where people get stuck, as which errors they find particularly confusing. (We could add a button to the online instance that says "this error message is unhelpful" to see where people feel truly stuck).

Why not do hands-on activities interspersed with the slides? Some participants will just "get it" and the activities will be easy for them, for others, it will be hard. If we did them interspersed we would have that awkward time when we ask “who needs more time” and half the hands go up … some people are bored, others are embarrassed that they're not done. Having time dedicated to hands-on learning gives the slow participants the time they need to finish a problem and get their questions answered. For the fast participants, we can have any number of really difficult things for them to work on and they get even more experience.

Activity 3 (15m)

What: A posttest containing 4-5 OxCaml programs in which we ask participants questions about mode annotations, error messages, unsafety, etc.

Why: The questions we ask will form the start of the "OxCaml Inventory," a set of questions that target the core concepts of OxCaml and test the conceptual model of the participants. This will give us a sense of where participants still have difficulty and what future tools/educational material should target. (Or maybe language changes?)