CS4215-project

A web-based explicit control evaluator for C

Overview

The C-interpreter project applies the notion of an explicit-control evaluator to the C programming language. Baseline expectations:

• Web-based implementation based on Source Academy frontend and js-slang

• Implementation of a sublanguage of C, consistent with a recent language specification

• Language constructs: variable and function declarations, blocks, conditionals statements and expressions, while loops

• Implementation should use an explicit-control evaluator, using a suitable abstraction for C's runtime stack.

• Memory management: the language needs to include heap allocation (malloc) and support pointer arithmetic and * and &.

Optional components:

• Visualization of heap and runtime stack

• Type checking

• Function pointers

sourc-slang

C language modified from js-slang.

Using sourc-slang in your local Source Academy

(sourc is the name of your language)

A common issue when developing modifications to js-slang is how to test it using your own local frontend. Assume that you have built your own frontend locally, here is how you can make it use your own sourc-slang, instead of the one that the Source Academy team has deployed to npm.

First, build and link your local sourc-slang: (don't forget to modify the "calc-slang" in both projects)

$ cd sourc-slang
$ yarn build
$ yarn link

Then, from your local copy of frontend:

$ cd frontend
$ yarn link "sourc-slang"

Then start the frontend and the new js-slang will be used.

Possible Issues (and manual solutions)

• If you failed to execute the jsdoc.sh in your bash
  • Delete the first line of jsdoc.sh (for Windows PowerShell) before executing yarn jsdoc.
  • Please modify the line break type if ‘bash\r’: No such file or directory
• node should be replaced by node.exe if you are using WSL with node.js installed on your Windows.
• In case you meet the same error as this when using node-getopt, modify the package.json of node-getopt as this PR shows.

Table of Contents

• CS4215-project
  • Overview
• sourc-slang
• Using sourc-slang in your local Source Academy
  • Possible Issues (and manual solutions)
• Table of Contents
• Requirements
• Documentation
• Requirements
• Testing
• Error messages
• Using your xx-slang in your local Source Academy
• Talks and Presentations
• License

Requirements

• node: known working version: v16.14.0

Documentation

Source is documented here: https://docs.sourceacademy.org/

Requirements

• bash: known working version: GNU bash, version 5.0.16
• latexmk: Version 4.52c
• pdflatex: known working versions
  • pdfTeX 3.14159265-2.6-1.40.18 (TeX Live 2017)

To build the documentation, run

$ git clone https://github.com/source-academy/calc-slang.git
$ cd calc-slang
$ yarn
$ yarn install
$ yarn jsdoc  # to make the web pages in calc-slang/docs/source
$ cd docs/specs
$ make        # to make the PDF documents using LaTeX

Note: The documentation may not build on Windows, depending on your bash setup, see above.

Documentation on the Source libraries are generated from inline documentation in the library sources, a copy of which are kept in docs/lib/*.js. The command yarn jsdoc generates the documentation and places it in the folder docs/source. You can test the documentation using a local server:

$ cd docs/source;  python -m http.server 8000

Documentation of libraries is displayed in autocomplete in the frontend. This documentation is generated by ./scripts/updateAutocompleteDocs.py and placed in src/editors/ace/docTooltip/*.json files. This script is run by yarn buildprior to tsc. To add a Source variant to the frontend autocomplete, edit src/editors/ace/docTooltip/index.ts and ./scripts/updateAutocompleteDocs.py.

Testing

js-slang comes with an extensive test suite. To run the tests after you made your modifications, run yarn test. Regression tests are run automatically when you want to push changes to this repository. The regression tests are generated using jest and stored as snapshots in src/\_\_tests\_\_. After modifying js-slang, carefully inspect any failing regression tests reported in red in the command line. If you are convinced that the regression tests and not your changes are at fault, you can update the regression tests as follows:

$ yarn test -- --updateSnapshot

Error messages

To enable verbose messages, have the statement "enable verbose"; as the first line of your program. This also causes the program to be run by the interpreter.

There are two main kinds of error messages: those that occur at runtime and those that occur at parse time. The first can be found in interpreter-errors.ts, while the second can be found in rules/.

Each error subclass will have explain() and elaborate(). Displaying the error will always cause the first to be called; the second is only called when verbose mode is enabled. As such, explain() should be made to return a string containing the most basic information about what the error entails. Any additional details about the error message, including specifics and correction guides, should be left to elaborate().

Please remember to write test cases to reflect your added functionalities. The god of this repository is self-professed to be very particular about test cases.

Using your xx-slang in your local Source Academy

(xx is the name of your language)

A common issue when developing modifications to js-slang is how to test it using your own local frontend. Assume that you have built your own frontend locally, here is how you can make it use your own xx-slang, instead of the one that the Source Academy team has deployed to npm.

First, build and link your local xx-slang: (don't forget to modify the "calc-slang" in both projects)

$ cd xx-slang
$ yarn build
$ yarn link

Then, from your local copy of frontend:

$ cd frontend
$ yarn link "xx-slang"

Then start the frontend and the new js-slang will be used.

Talks and Presentations

• How js-slang works under the hood [17th Jan 2023][The Gathering][slides]

License

All sources in this repository are licensed under the Apache License Version 2.