This function evaluates all B-spline basis functions at the position
x and stores them in the vector B, so that the i-th element
is B_i(x). The vector B must be of length
n = nbreak + k - 2. This value may also be obtained by calling
Computing all the basis functions at once is more efficient than
computing them individually, due to the nature of the defining
This function evaluates all potentially nonzero B-spline basis functions at the position x and stores them in the vector Bk, so that the i-th element is B_(istart+i)(x). The last element of Bk is B_(iend)(x). The vector Bk must be of length k. By returning only the nonzero basis functions, this function allows quantities involving linear combinations of the B_i(x) to be computed without unnecessary terms (such linear combinations occur, for example, when evaluating an interpolated function).
This function returns the number of B-spline coefficients given by n = nbreak + k - 2.