Type-checking code for the Grace Programming Language from Pomona College.

Usage

Prerequisites

Node.js is a prerequisite to use Grace. At the time when this document was written, version v10.15.3 was being used.

Node.js

Installation

To install Grace, clone the git repository mentioned below, change your directory to be the newly created StaticTyping folder, and then run the chmod command as shown below:

git clone https://github.com/KimBruce/StaticTyping.git
cd StaticTyping
chmod +x install-minigrace.sh
./install-minigrace.sh

Environment variables

Open the .bash_profile, and set the GRACE_MODULE_PATH to /usr/local/lib/grace/modules and the directory StaticTyping on your machine.

Compiling

To compile after any changes are made to the static typing files, change your directory into the StaticTyping folder and run a make or make compile command.

Testing

To run all the tests at once, you can run the make test command in the StaticTyping directory.

Implementation status

Unsupported features

• Dialects
• Traits
• Generic constraints
• Standard grace objects from prelude (currently hard coded)

Supported features

• Generics without constraints
• Subtyping
  • & and variant types using normal form
• Imports
  • Generics
  • Chained (imports of imports)

Details

Dialects

We could not figure out how to use StaticTyping dialect alongside a user-defined dialect. We tried two different approaches:

1. Create a hasTypecheck boolean field in util.grace and set it to true when --typecheck option is present. Then, in compiler.grace, if hasTypecheck is true, call the visitor from StaticTyping.grace. The issue we had with this approach is that mgc was not able to locate StaticTyping.js.
2. Manually combine a user-defined dialect and StaticTyping.grace in a single .grace file.

Subtyping optimization

We have not implemented subtyping optimization. That is, a type Number | String | Number should reduce to Number | String type, but currently does not. Our proposed changes can be found in TODO comment in method | in ObjectTypeModule.grace.

Embedded types

We have implemented a representation of embedded types, but have decided not to commit that change since the language specification does not allow types inside types. That code can be found here. The main changes include adding types method to anObjectType and types parameter to fromMethods method in ObjectTypeModule.grace.