add amy reference compiler

amy_reference_compiler.md

+====== The Amy Reference Compiler ======
+
+We provide you with a reference compiler for the Amy language that you can use to explore the expected behavior of your own compiler.
+
+The reference compiler is [[http://lara.epfl.ch/~gschmid/clp20/amyc_2.12-1.7.jar|available here]].
+
+You can run it as follows:
+  java -cp amyc_2.12-1.7.jar amyc.Main [options] [input files]
+
+To see the list of available options do 
+  java -cp amyc_2.12-1.7.jar amyc.Main --help
+
+The easiest way to execute a program is to run it in ''-''''-interpret'' mode. If you want to generate WebAssembly binary code, you should follow these steps:
+  * Install ''nodejs''. We have tested amyc with Node version 12, though other versions might work. See the [[https://nodejs.org/en/|Node website]] for installation instructions.
+  * Make sure the ''wat2wasm'' executable is visible, i.e., it is in the system path or, for Linux or Mac, you are at the toplevel of the ''amyc'' directory.
+  * Run ''npm install deasync'' in the directory you plan to run ''amyc''.
+  * Run ''amyc'' without options. You will get a few output files.
+  * Run ''nodejs <output file>.js''
+
+
+===== Bug Reports =====
+
+We welcome bug reports! Please use the forum on Moodle for this purpose.
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