TOMS446 is a C library which implements ACM TOMS algorithm 446, for the manipulation of Chebyshev series.
While the text of many ACM TOMS algorithms is available online through ACM: http://www.acm.org/pubs/calgo or NETLIB: http://www.netlib.org/toms/index.html, most of the early algorithms are not available. This is one of them. I typed it in.
The computer code and data files described and made available on this web page are distributed under the GNU LGPL license.
TOMS466 is available in a C++ version and a C++ version and a FORTRAN77 version and a FORTRAN90 version and a MATLAB version.
BERNSTEIN, a C library which evaluates the Bernstein polynomials, useful for uniform approximation of functions;
CHEBYSHEV, a C library which computes the Chebyshev interpolant/approximant to a given function over an interval.
CHEBYSHEV_SERIES, a C library which can evaluate a Chebyshev series approximating a function f(x), while efficiently computing one, two or three derivatives of the series, which approximate f'(x), f''(x), and f'''(x), by Manfred Zimmer.
DIVDIF, a C library which computes interpolants by divided differences.
HERMITE, a C++ library which computes the Hermite interpolant, a polynomial that matches function values and derivatives.
SPLINE, a C library which can construct and evaluate spline interpolants and approximants.
TEST_APPROX, a C library which defines test functions for approximation and interpolation.
You can go up one level to the C source codes.