Evaluating expression and operators (Refs #51)[2]

* new files: py_visitor, py_utils, py_operators - to support needs for
  py_visitor for now, usage of any for loose type checks for now
* py-interpreter - replaced dummy with PyVisitor
* py_visitor - rework visit*expr to work with ExprNS and FileInputStmt
* py_utils - reworked operandTranslator to work with TokenType
* py_operators - reworked to change es.UnaryOperator to TokenType

Author: lucasnyc

src/cse-machine/py_interpreter.ts

@@ -2,14 +2,15 @@ import { Context } from "./context";
 import { CSEBreak, Representation, Result, Finished } from "../types";
 import { StmtNS } from "../ast-types";
 import { Value, ErrorValue } from "./stash";
+import { PyVisitor } from "./py_visitor";
 
 type Stmt = StmtNS.Stmt;
 
 export function PyCSEResultPromise(context: Context, value: Value): Promise<Result> {
     return new Promise((resolve, reject) => {
         if (value instanceof CSEBreak) {
             resolve({ status: 'suspended-cse-eval', context });
-        } else if (value.type === 'error') {
+        } else if (value && value.type === 'error') {
             const errorValue = value as ErrorValue;
             const representation = new Representation(errorValue.message);
             resolve({ status: 'finished', context, value, representation } as Finished);
@@ -22,6 +23,7 @@ export function PyCSEResultPromise(context: Context, value: Value): Promise<Resu
 
 export function PyEvaluate(code: string, program: Stmt, context: Context): Promise<Result> {
     // dummy for now, just to test getting AST from parser
-    const dummyValue = { type: 'NoneType', value: undefined };
-    return PyCSEResultPromise(context, dummyValue);
+    const visitor = new PyVisitor(code, context);
+    const result = visitor.visit(program);
+    return PyCSEResultPromise(context, result);
 }