It's often a better design to keep the parts that are largely set/need to be efficient in a "hard" language like C (or something like Common Lisp with type annotations), but keep the parts that need to be flexible in a "soft" language like an embedded Lua, Python, or Scheme, etc. You don't have to use just one language.

http://c2.com/cgi/wiki?AlternateHardAndSoftLayers