Shared C++ Backend for Approximate Bayesian Computation

Provides a compact C++ backend for Approximate Bayesian Computation (ABC) with a thin R frontend. The current implementation is primarily a C++ reimplementation of offline ABC workflows provided by the R 'abc' package , with the public R interface intentionally kept small and centered on abc() and summary() methods. The computational work is performed by shared C++ code. In addition to reproducing common 'abc' workflows, the package adds optional dimensionality reduction of summary statistics through Principal Component Analysis (PCA) and Partial Least Squares (PLS), following related ideas described by Bazin et al. (2010) and Wegmann et al. (2009) .