Release Notes

v1.1 This version takes the vanilla implementation using the Visitor design pattern and creates a generic Repl that can use the command line to determine which Visitor the user wants to use. Specific changes:

• Visitor interface now includes a getDefaultState() method

• PersistentWalker class now provides for a visitor that will retain the same instance of a state across multiple traversals of ASTs. This allows for multiple user-entered expressions to interact with each other (e.g. previous statements can modify a global environment to affect future evaluations)

• Created VisitException class to better facilitate the separation of sources of errors that arise while lexing, parsing and walking user input. (For an evaluator, WalkException is a runtime error).

• Renamed Repl to Main. Rewrote it to create a generic instance of PersistentWalker wrapped around a visitor of a class specified on the command line

• There are two known visitor classes at this time: Evaluator and ToScheme.

Example Usages:

• To use as a Repl for a standard interpretor (expression evaluator):

  $(JAVA_EXEC) Main -w Evaluator - OR more simply: $(JAVA_EXEC) Main -

• To use as a converter to Scheme (prefix notation for expressions):

  $(JAVA_EXEC) Main -w ToScheme -

• To evaluate a file of expressions called foo.txt:

  $(JAVA_EXEC) Main -w Evaluator foo.txt OR more simply: $(JAVA_EXEC) Main foo.txt