Roll Observatory packages and add a roll script

petitparser/lib/lisp.dart

-/**
- * This package contains a simple grammar and evaluator for LISP.
- *
- * The code is reasonably complete to run and evaluate reasonably complex
- * programs from the console and from the web browser.
- */
-library lisp;
-
-import 'dart:collection';
-import 'package:petitparser/petitparser.dart';
-
-part 'src/lisp/cons.dart';
-part 'src/lisp/environment.dart';
-part 'src/lisp/grammar.dart';
-part 'src/lisp/name.dart';
-part 'src/lisp/natives.dart';
-part 'src/lisp/parser.dart';
-part 'src/lisp/standard.dart';
-
-/** The standard lisp parser definition. */
-final lispParser = new LispParser();
-
-/** The evaluation function. */
-eval(Environment env, expr) {
-  if (expr is Cons) {
-    return eval(env, expr.head)(env, expr.tail);
-  } else if (expr is Name) {
-    return env[expr];
-  } else {
-    return expr;
-  }
-}
-
-/** Evaluate a cons of instructions. */
-evalList(Environment env, expr) {
-  var result = null;
-  while (expr is Cons) {
-    result = eval(env, expr.head);
-    expr = expr.tail;
-  }
-  return result;
-}
-
-/** The arguments evaluation function. */
-evalArguments(Environment env, args) {
-  if (args is Cons) {
-    return new Cons(eval(env, args.head), evalArguments(env, args.tail));
-  } else {
-    return null;
-  }
-}
-
-/** Reads and evaluates a [script]. */
-evalString(Parser parser, Environment env, String script) {
-  var result = null;
-  for (var cell in parser.parse(script).value) {
-    result = eval(env, cell);
-  }
-  return result;
-}