toms886, a Fortran90 code which implements an interpolation procedure based on "Padua points", defined in the square [-1,+1]^2, whose interpolating power is especially good. It is possible to map these points to the general rectangle, ellipse or triangle to do interpolation on these regions as well.
The text of many ACM TOMS algorithms is available online through ACM: https://calgo.acm.org/ or NETLIB: https://www.netlib.org/toms/index.html.
The information on this web page is distributed under the MIT license.
toms886 is available in a C version and a C++ version and a Fortran90 version and a MATLAB version and an Octave version.