23.4. Interpreter Modifications¶
23.4.1. Overview of Exercises¶
The following review problems are designed to help you prepare for the exercises that you will complete in class on Monday. These exercises will consequently set the stage for your next assignment. In each one of these in-class exercises as well as in the upcoming assignments, you will have to extend the SLang interpreter. Recall that the interpreter is made up of the following files:
- absyn.js defines the abstract syntax of SLang 1.
- grammar.jison defines the lexical-level grammar and the phrase-structure grammar for SLang 1; this file also contains the parser code that builds the AST.
- env.js implements the data structure that represents the environment of the interpreter; this file also defines the types of denoted values, that is, those that can appear in the environment.
- interpreter.js implements the interpreter itself.
In each one of the following problems, we describe an extension to the interpreter that you will carry out in class. Read carefully how each extension is supposed to behave when interpreted, and assume that we will carry out the extensions in the order that they appear here. Then select all of those files that MUST be modified from what they were in the prior problem to carry out the described extension. For each file that you check, be prepared to give an overview of the changes that would need to be made in that file.
