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+# Rust λ-calcul reference implementation
+
+This directory contains a reference implementation of a normal order semantics λ-calculus based language.
+Current syntax is based on S-expressions, ie. Lisp. There is a command-line interpreter for batch and interactive evaluation of input, and an embryonic tester daemon.
+
+# Tester
+
+**NOTE**: This is a work-in-progress, current tester is only capable of running program locally through a forked process
+
+The tester daemon is inspired by [Extreme Startup](https://github.com/rchatley/extreme_startup): It's a REST-ish server and client that allows to repeatedly send λ-terms to a remote execution engine and compare the result against its expectations.
+
+The interaction flow is simple:
+
+* The server listens on a well-known port
+* A client connects to this port and requests a test session (`POST /register`), giving a URL to callback,
+* The server returns an identification token, to passed to and from the client in subsequent calls,
+* Then the server repeatedly sends requests to the client (`POST /eval`) whose body is a S-expr representing a λ-term, and it expects an evaluation result.
+  * Note the evaluation can return error if the term is syntactically malformed
+  * The server waits at most 60 seconds for the answer
+* If the client fails to answer, or answers wrongly, the server keeps sending the same request
+* If the client's answer is correct, the server sends another term, more complex, to evaluate.