From 6e83f1c0f6d38035af051b4a80cc2243cb97e9f1 Mon Sep 17 00:00:00 2001
From: "Marten H. van Kerkwijk" <mhvk@astro.utoronto.ca>
Date: Thu, 27 Feb 2025 14:35:34 -0500
Subject: [PATCH] Add install from source instructions

---
 quaddtype/README.md | 36 ++++++++++++++++++++++++++++++++++++
 1 file changed, 36 insertions(+)

diff --git a/quaddtype/README.md b/quaddtype/README.md
index 60693cb..bd06738 100644
--- a/quaddtype/README.md
+++ b/quaddtype/README.md
@@ -20,3 +20,39 @@ np.array([1,2,3], dtype=QuadPrecDType("sleef"))
 # using longdouble backend
 np.array([1,2,3], dtype=QuadPrecDType("longdouble"))
 ```
+
+## Install from source
+
+The code needs the quad precision pieces of the sleef library, which
+is not available on most systems by default, so we have to generate
+that first.  The below assumes one has the required pieces to build
+sleef (cmake and libmpfr-dev), and that one is in the package
+directory locally.
+
+```
+git clone https://github.com/shibatch/sleef.git
+cd sleef
+cmake -S . -B build -DSLEEF_BUILD_QUAD:BOOL=ON -DSLEEF_BUILD_SHARED_LIBS:BOOL=ON -DCMAKE_POSITION_INDEPENDENT_CODE=ON
+cmake --build build/ --clean-first -j
+cd ..
+```
+
+In principle, one can now install this system-wide, but easier would
+seem to use the version that was just created, as follows:
+```
+export SLEEF_DIR=$PWD/sleef/build
+export LIBRARY_PATH=$SLEEF_DIR/lib
+export C_INCLUDE_PATH=$SLEEF_DIR/include
+export CPLUS_INCLUDE_PATH=$SLEEF_DIR/include
+python3 -m venv temp
+source temp/bin/activate
+pip install meson-python numpy pytest
+pip install -e . -v --no-build-isolation
+export LD_LIBRARY_PATH=$SLEEF_DIR/lib
+```
+
+Here, we created an editable install on purpose, so one can just work
+from the package directory if needed, e.g., to run the tests with,
+```
+python -m pytest
+```