[R] calling R from C or C++

[Bahoo]

Hi,

I have C/C++ code from which I wish I could call R to
do something useful.

I saw a 2003 message by Thomas saying that "You can
compile R as a shared library, which allows you to
construct and evaluate R expressions from C."  Any
more information would be helpful.  I am looking for
some documentation that has a more step by step like
instructions.  Anyone who has experience, please point
me to some resources.

ps. There is a document on CRAN named "Writing R
extensions" which seems relevant, but it was too
difficult for me to understand.

Thanks in advance!