updated lis.py examples

02-array-seq/lispy/README.md

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+# Norvig's originals and updates
+
+This directory contains:
+
+* `original/`:
+Norvig's [`lis.py`](https://github.com/norvig/pytudes/blob/c33cd6835a506a57d9fe73e3a8317d49babb13e8/py/lis.py),
+[`lispy.py`](https://github.com/norvig/pytudes/blob/c33cd6835a506a57d9fe73e3a8317d49babb13e8/py/lispy.py), and the `lispytest.py` custom test script for testing both;
+* `py3.10/`: `lis.py` with type hints, pattern matching, and minor edits—requires Python 3.10.
+
+The `py3.10/` directory also has `lis_test.py` to run with
+[pytest](https://docs.pytest.org), including all the
+[`lis_tests` suite](https://github.com/norvig/pytudes/blob/60168bce8cdfacf57c92a5b2979f0b2e95367753/py/lispytest.py#L5)
+from `original/lispytest.py`,
+and additional separate tests for each expression and special form handled by `evaluate`.
+
+
+## Provenance, Copyright and License
+
+`lis.py` is
+[published](https://github.com/norvig/pytudes/blob/c33cd6835a506a57d9fe73e3a8317d49babb13e8/py/lis.py)
+in the [norvig/pytudes](https://github.com/norvig/pytudes) repository on Github.
+The copyright holder is Peter Norvig and the code is licensed under the
+[MIT license](https://github.com/norvig/pytudes/blob/60168bce8cdfacf57c92a5b2979f0b2e95367753/LICENSE).
+
+
+## Changes to Norvig's code
+
+I made small changes to the programs in `original/`:
+
+* In `lis.py`:
+  * The `Procedure` class accepts a list of expressions as the `body`, and `__call__` evaluates all those expressions in order, returning the value of the last. This is consistent with Scheme's `lambda` syntax and provided a useful example for pattern matching.
+  * In the `elif` block for `'lambda'`, I added the `*` in front of the `*body` variable in the tuple unpacking to capture the expressions as a list, before calling the `Procedure` constructor.
+
+* In `lispy.py` I made [changes and a pull request](https://github.com/norvig/pytudes/pull/106) to make it run on Python 3.
+
+_Luciano Ramalho<br/>June 29, 2021_