Architecture

The following are Pratt parsers in increasing levels of expressiveness:

• 1-infix.py just does infix
• 2-prefix.py adds prefix parsing
• 3-juxt.py adds implicit * juxtapose
• 4-paren.py adds parethesis grouping and function application

They are meant to be looked at in order using diff to see the changes introduced. I have spent a lot of time making it as intelligible as possible so hopefully no explanation is necessary.

Run tests with test.py. It will print the commandline args it needs with python test.py -h.

Finally, cons.py has definitions of Atom and Cons which we build our syntax tree from (like lisp).

Syntax

The return value from parse in each parser will stringify as an S-expression. You might notice some strange operators in the output, like $ and |. Those are function and operator application. You can remove them and get normal lispy S-expressions with strip_apps() in test.py. The sexp() function in test.py will automatically do this.

If you want another stringification, checkout the test.py which also has RPN, python, and fully parenthesized syntax.

missing:

• := assignment (right assoc)

• f(x,y) functions of multiple args

• >= > < <= comparison

• == != && || boolean operators

• {1, 2, 3} sets, vector [1, 2, 3]

• \in \subset \union \intersection \difference \disjoint-union (or +) set ops

• statements (function calls, assignment): everything else should be an expression.