README.md

A Collection of Novice Interactions with the OCaml Top-Level System

We recruited around 50 students each across two instances of the CSE 130 (Undergraduate Programming Languages) course at UC San Diego (IRB #140608) to use an instrumented version of the ocaml-top editor, which logged each of their interactions with the top-level system while they worked on the first three homework assignments.

We have released this data as a CC0 work, you are free to use it for your own research or however else you please. We just ask that if your use leads to a publication, please cite the dataset as follows.

@misc{yunounderstand,
  author       = {Eric L Seidel and Ranjit Jhala},
  title        = {A Collection of Novice Interactions with the {OCaml} {Top-Level} System},
  month        = jun,
  year         = 2017,
  doi          = {10.5281/zenodo.806814},
  url          = {https://doi.org/10.5281/zenodo.806814}
}

Raw Data

Each JSON file in data/raw/{sp14,fa15}/ contains an object of the following form on each line. Note that this means the file as a whole is NOT valid JSON, each line must be parsed individually as a JSON object.

{
    "file": "hw1.ml" | "hw2.ml" | "hw3.ml",
    "time": number,
    "body": string,
    "cursor": number,
    "event": {
        "type": "abort" | "eval" | "stop",
        "region": {
            "start": number,
            "stop": number
        }
    },
    "ocaml": [{
        "in": string,
        "out": string,
        "type": "scope" | "syntax" | "type" | "",
        "min": string
    }]
}

The "file" field is the name of the file and should be one of "hw1.ml", "hw2.ml", or "hw3.ml". The "time" field is the UNIX timestamp of the event. The "body" field is the contents of the file at that point. The "cursor" field tracks the location of the cursor as an offset into the body.

The "event" field describes what type of event occurred. The possibilities for the "type" field are:

• "abort": the student aborted the current computation, i.e. sent a SIGINT to the top-level.
• "eval": the student sent some definitions to be evaluated. In this case the "event" field will also contain a "region" object with "start" and "stop" offsets into the body, indicating what program text was evaluated.
• "stop": the student restarted the top-level.

In the case of an "eval" event, the object will also contain an "ocaml" array, which contains the list of definitions that were sent to the OCaml top-level. Each item in the list is an object containing:

• "in": a single definition sent to OCaml.

• "out": OCaml's response. We only captured the error responses, so this field will often be empty.

• "type": a classification of the response. "scope" indicates an unbound variable error, "syntax" a syntax error, and "type" a type error. The empty string implies there was no error.

• "min": a self-contained program with the minimal set of definitions. This is extremely useful because the students were interacting with the OCaml interpreter rather than the compiler, and would send individual (groups of) definitions to the interpreter rather than compiling the entire file. Thus, we cannot expect the contents of the "in" field to constitute a complete, closed program.

  We were not always able to produce such a minimal program, so this field will sometimes be empty.

NOTE: the offsets into the body ("cursor", "start", and "stop") are not always reliable, we have observed cases where they do not match up with the actual text that was sent to OCaml.

Derived Data

We include two derived datasets.

1. A collection of distinct, minimal (i.e. derived from the "min" field above), ill-typed programs, located in data/derived/{sp14,fa15,comb}/prog, extracted from the SP14 (resp. FA15 and combined) dataset. The programs are further grouped into cnstr and unify folders. The cnstr folder contains programs with errors that are explained pretty well by OCaml (e.g. "This constructor takes 3 arguments but only 2 were supplied"). The unify folder contains more general unification errors, which is the vast majority.

   For convenience, each .ml file is paired with a .ml.out file containing the OCaml compiler's error message, and a .orig.ml file containing the unminimized program (i.e. the "body" field above).

   These programs are produced by the python3 script scripts/extract_programs.py. We provide Makefile targets progs{-fa15,-sp14,-comb} for convenience.

2. A collection of ill-typed programs paired with their subsequent fixes, located in data/derived{sp14,fa15}/pairs.json. These files are again a sequence of JSON objects on each line, with the following structure:

   {
       "index": number,
       "hw": "hw1" | "hw2" | "hw3",
       "problem": string,
       "bad": string,
       "fix": string
   }
   

   The "hw" and "problem" fields specify which homework and problem the student was working on. The "bad" field contains the ill-typed program, and the "fix" field contains the student's fix. We define a "fix" to an ill-typed program as the first subsequent program the student submitted to the interpreter that (1) we can determine to be solving the same homework problem, and (2) has the correct type. Both "bad" and "fix" contain the minimal programs from the "min" field above.

   We determine which homework problem a program is solving by looking at the names of the defined functions (this works because the programs are already minimized). We determine whether a fix is valid by checking that it has the expected type (we, of course, know the expected types of all homework programs).

   These programs are produced by the python3 script scripts/extract_pairs.py. We provide Makefile targets pairs{-fa15,-sp14} for convenience. NOTE: extract_pairs.py expects ocaml to be on your PATH as it will check that the "fixes" typecheck against the expected type for each homework problem.