install s2geometry (c++ libs) on mac with brew / plus hello world s2geometry example

Install-darwin-brew-s2geometry.txt

# based on: https://s2geometry.io/about/platforms
# note: set -DOPENSSL_ROOT_DIR instead of -DOPENSSL_INCLUDE_DIR

brew install gflags glog openssl
brew install cmake

# Download Googletest release 1.8.0 and unpack it in a directory of your choosing.
# (Take note of this directory as you will need to point CMake to it.)
# https://github.com/google/googletest/releases/tag/release-1.8.0

# find where brew installed openssl (such as /usr/local/Cellar/openssl@1.1/1.1.1l)
# maybe use: brew --prefix openssl

git clone git@github.com:google/s2geometry.git
cd s2geometry

mkdir build
cd build

cmake \
  -DWITH_GFLAGS=ON \
  -WITH_GTEST=ON \
  -DGTEST_ROOT=/code/google/googletest/googletest-release-1.8.0/googletest \
  -DOPENSSL_ROOT_DIR=/usr/local/Cellar/openssl@1.1/1.1.1l \
  ..

make -j8
make install

main.cpp

#include "s2/s2point.h"
#include "s2/s2cell_id.h"

using namespace std;

int main()
{
    S2Point v0 = S2Point(1, 1, 0);
    cout<<v0<<endl;

    S2CellId id = S2CellId(v0);
    cout<<id<<endl;

    return 0;
}

Makefile

CXX=g++
CXXFLAGS=-std=c++11 -stdlib=libc++
LDLIBS=-ls2
OBJS=main.cpp

build: $(OBJS)
	$(CXX) $(LDLIBS) $(CXXFLAGS) -o app $(OBJS)

run: build
	./app

output.txt

make run
g++ -ls2 -std=c++11 -stdlib=libc++ -o app main.cpp
./app
[1, 1, 0]
1/322222222222222222222222222222