doc: + README.md

README.md

@@ -0,0 +1,55 @@
+# simulator library
+
+in-memory deterministic simulator
+
+## Getting Started
+
+### build + install dependencies
+
+build+install these first
+
+- xo-reactor [github.com/Rconybea/xo-reactor](https://github.com/Rconybea/xo-reactor)
+- xo-ordinaltree [github.com/Rconybea/xo-ordinaltree](https://github.com/Rconybea/xo-ordinaltree)
+
+### build + install xo-simulator
+```
+$ cd xo-simulator
+$ mkdir build
+$ cd build
+$ INSTALL_PREFIX=/usr/local  # or wherever you prefer
+$ cmake -DCMAKE_MODULE_PATH=${INSTALL_PREFIX}/share/cmake -DCMAKE_PREFIX_PATH=${INSTALL_PREFIX} -DCMAKE_INSTALL_PREFIX=${INSTALL_PREFIX} ..
+$ make
+$ make install
+```
+(also see .github/workflows/main.yml)
+
+### build for unit test coverage
+```
+$ cd xo-simulator
+$ mkdir ccov
+$ cd ccov
+$ cmake -DCMAKE_MODULE_PATH=${INSTALL_PREFIX}/share/cmake  -DCMAKE_PREFIX_PATH=${INSTALL_PREFIX} -DCODE_COVERAGE=ON -DCMAKE_BUILD_TYPE=Debug ..
+```
+
+## Development
+
+### LSP support
+
+LSP looks for compile commands in the root of the source tree;
+cmake creates them in the root of its build directory.
+
+```
+$ cd xo-simulator
+$ ln -s build/compile_commands.json
+```
+
+### display cmake variables
+
+- `-L` list variables
+- `-A` include 'advanced' variables
+- `-H` include help text
+
+```
+$ cd xo-simulator/build
+$ cmake -LAH
+```