Add 'xo-expression/' from commit '5ac3c03a0c'

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xo-expression/README.md

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+# xo-expression library
+
+A library for representing abstract syntax trees for EGAD (a small expression-based language).
+See also
+- [github/Rconybea/xo-jit](https://github.com/Rconybea/xo-jit)
+  EGAD code generation via LLVM
+- [github/Rconybea/xo-pyexpression](https://github.com/Rconybea/xo-pyexpression)
+  build EGAD expressions from a python session
+- [github/Rconybea/xo-pyjit](https://github.com/Rconybea/xo-pyjit)
+  compile + run EGAD expressions from a python session
+
+## Getting Started
+
+### build + install `xo-cmake` dependency
+
+- [github/Rconybea/xo-cmake](https://github.com/Rconybea/xo-cmake)
+
+Installs a few cmake ingredients,  along with a build assistant `xo-build` for XO projects such as this one.
+
+### build + install other XO dependencies
+```
+$ xo-build --clone --configure --build --install xo-indentlog
+$ xo-build --clone --configure --build --install xo-refnct
+$ xo-build --clone --configure --build --install xo-subsys
+$ xo-build --clone --configure --build --install xo-reflect
+```
+
+Note: can use `xo-build -n` to dry-run here
+
+### copy `xo-expression` repository locally
+```
+$ xo-build --clone xo-expression
+```
+
+or eqivalently
+```
+$ git clone git@github.com:Rconybea/xo-expression.git
+```
+
+### build + install xo-expression
+```
+$ xo-build --configure --build --install xo-expression
+```
+
+or equivalently:
+```
+$ PREFIX=/usr/local  # or wherever you prefer
+$ cmake -DCMAKE_INSTALL_PREFIX=${PREFIX} -S xo-expression -B xo-jit/.build
+$ cmake --build xo-expression/.build
+$ cmake --install xo-expression/.build
+```
+
+### build for unit test coverage
+```
+$ cmake -DCMAKE_BUILD_TYPE=coverage -DCMAKE_INSTALL_PREFIX=$PREFIX xo-expression/.build-ccov
+$ cmake --build xo-expression/.build-ccov
+```
+
+### LSP support
+```
+$ cd xo-expression
+$ ln -s build/compile_commands.json  # lsp will look for compile_commands.json in the root of the source tree
+```