I need something to embed in my C/C++ program to interpret formulas of the like x*log(x) or sin(x). I would like something small and simple, otherwise I can just embed Python, or Ch, or Scheme, or you name it. But all I need is simple formulas. I have searched the web without luck. Although I don't require it, performance (e.g., the use of a simple JIT) would be a bonus.
Lua - is by far the simplest to embed and use and there is a very small and very fast version with a JIT: http://luajit.org/