A Scheme Interprester built in Scheme to interpret Scheme.
David Lam
Adam Finer
There are two branches: master and pass-by-reference.
The master branch contains most major milestone work for the class. The pass-by-reference branch contains an experimental feature in which our interpreter allowed the usage of 2 unique features not native to scheme: passing-by-reference and lexical addressing. To accomplish this, our interpreter heavily uses the ADT chez-scheme provides: Box.
Passing-by-reference feature allows an individual to create a scheme procedure such that certain parameters were to be taken as references rather than values. We accomplished this by creating a special parameter datatype and updating our parser to handle ref procedure parameters (i.e. (lambda ((ref x)) ...)). We also updated our environment datatype to store a vector of Boxes. Therefore, whenver our closures required a ref parameter, it would be passed the Box itself. Otherwise, the parameter would get the value within the box instead.
As for lexical addressing, we simply updated our parsing pipeline. After parsing the inital expressions and syntax expanding the parsed expressions, we then lexically addressed the expanded expression before attempting to evaluate it. This served to help improve our lookup time as we now know the lexical depth and lexical position within the chains of local environments or global environment if the variable was free.
As the project grew, it became obnoxious to zip the proper files to turn it in to the grading server. To overcome this entirely, David wrote zip.js, a NodeJS script, that will find all .ss or .scm files within a specified source directory and zip it all up into interpreter.zip.
To zip the files, run the following command:
node zip.js <source_directory>
Currently, this repo is setup with an npm scripts that will default the source_directory to be src. To execute this, run the following command:
npm start