Rewrite README.md

README.md

@@ -1,21 +1,28 @@
 # Go-Cpp #
 
-This project demonstrates how to make Go programs call C++ facilities.
+This project demonstrates how to call C++ code from Go program without
+the need of using SWIG.
 
 The basic idea is to write a
 [C wrapper](https://github.com/wangkuiyi/go-cpp/tree/master/c%2B%2B/c%2B%2B_interface_lib)
-of the
-[C++ facilities](https://github.com/wangkuiyi/go-cpp/tree/master/c%2B%2B/c%2B%2B_static_lib),
+of
+[C++ code](https://github.com/wangkuiyi/go-cpp/tree/master/c%2B%2B/c%2B%2B_static_lib),
 and use `cgo` to call this C wrapper.
 
-However, it is known that C programs cannot call C++ facilities.  The
-trick is to write the wrapper in C++, so it can contain some C
-functions defined using `extern "C"`; and exports only these C
-functions to `cgo`.
+## Checkout and Build
 
-It is also notable that `cgo` allows Go programs to call C functions
-in shared libraries only.  So we need to build the wrapper as a shared
-library.  To do so, we build the C++ facilities into a static library,
-which is then linked into the wrapper (shared) library.
+    git clone -b develop https://github.com/wangkuiyi/go-cpp
+    cd go-cpp/c++
+    scons
+    cd ../go
+    export GOPATH=`pwd`
+    cd src/go_prog
+    go install
+    DYLD_LIBRARY_PATH=$GOPATH/../c++/ $GOPATH/bin/go_prog
 
-In this example project, we use `SCons` to build C++ code.
+Note that you need to install SCons to build the C++ part.  In order
+to install SCons on Mac OS X, you can use Homebrew.
+
+If you are using Linux, the last command to run the demo program is:
+
+    LD_LIBRARY_PATH=$GOPATH/../c++/ $GOPATH/bin/go_prog