Lagrange Interpolation - need help

I am looking to write a program to implement Lagrange Polynomial Interpolation! I want to interpolate exp(-x^2) and 1/1+x^2. I also want to test the code using the following node list {-5,-4,-3,-2,-1,0,1,2,3,4,5} and estimate the value of the functions above from -5 to 5 at 0.1 steps. I am ok at C programming but basic code is preferable! Any help with the actual method using C would be appreciated!! Thanks in advance!!

I take it you've seen: Interpolation/Lagrange ?