Small-angle scattering data analysis for dense polydisperse systems: The FLAC program. The problem is the calculation of the scattering cross section in small-angle scattering of polydisperse neutral and charged hard spheres. Both dense or dilute systems are considered. The algorithms implemented here are obtained by solving the Orstein-Zernike integral equations within the Percus-Yevick or mean spherical approximation closures for neutral or charged hard spheres.