Rcpp11 includes a header only C++11 library that facilitates 
  integration between R and modern C++.

Provides optimized functions and flexible iterators implemented in
    C++ for solving problems in combinatorics and computational mathematics.
    Handles various combinatorial objects including combinations, permutations,
    integer partitions and compositions, Cartesian products, unordered
    Cartesian products, and partition of groups. Utilizes the RMatrix class
    from 'RcppParallel' for thread safety. The combination and permutation
    functions contain constraint parameters that allow for generation of all
    results of a vector meeting specific criteria (e.g. finding all
    combinations such that the sum is between two bounds). Capable of
    ranking/unranking combinatorial objects efficiently (e.g. retrieve only the
    nth lexicographical result) which sets up nicely for parallelization as
    well as random sampling. Gmp support permits exploration where the total
    number of results is large (e.g. comboSample(10000, 500, n = 4)).
    Additionally, there are several high performance number theoretic
    functions that are useful for problems common in computational mathematics.
    Some of these functions make use of the fast integer division library
    'libdivide'. The primeSieve function is based on the segmented sieve of
    Eratosthenes implementation by Kim Walisch. It is also efficient for large
    numbers by using the cache friendly improvements originally developed by
    Tomás Oliveira. Finally, there is a prime counting function that implements
    Legendre's formula based on the work of Kim Walisch.

'Annoy' is a small C++ library for Approximate Nearest Neighbors 
 written for efficient memory usage as well an ability to load from / save to
 disk. This package provides an R interface by relying on the 'Rcpp' package,
 exposing the same interface as the original Python wrapper to 'Annoy'. See
 <https://github.com/spotify/annoy> for more on 'Annoy'. 'Annoy' is released
 under Version 2.0 of the Apache License. Also included is a small Windows
 port of 'mmap' which is released under the MIT license.