The Rcpp package provides R functions as well as a C++ library which facilitate the integration of R and C++. . R data types (SEXP) are matched to C++ objects in a class hierarchy. All R types are supported (vectors, functions, environment, etc ...) and each type is mapped to a dedicated class. For example, numeric vectors are represented as instances of the Rcpp::NumericVector class, environments are represented as instances of Rcpp::Environment, functions are represented as Rcpp::Function, etc ... The "Rcpp-introduction" vignette provides a good entry point to Rcpp. . Conversion from C++ to R and back is driven by the templates Rcpp::wrap and Rcpp::as which are highly flexible and extensible, as documented in the "Rcpp-extending" vignette. . Rcpp also provides Rcpp modules, a framework that allows exposing C++ functions and classes to the R level. The "Rcpp-modules" vignette details the current set of features of Rcpp-modules. . Rcpp includes a concept called Rcpp sugar that brings many R functions into C++. Sugar takes advantage of lazy evaluation and expression templates to achieve great performance while exposing a syntax that is much nicer to use than the equivalent low-level loop code. The "Rcpp-sugar" vignette gives an overview of the feature. . Rcpp attributes provide a high-level syntax for declaring C++ functions as callable from R and automatically generating the code required to invoke them. Attributes are intended to facilitate both interactive use of C++ within R sessions as well as to support R package development. Attributes are built on top of Rcpp modules and their implementation is based on previous work in the inline package. . Many examples are included, and over 870 unit tests in over 400 unit test functions provide additional usage examples. . An earlier version of Rcpp, containing what we now call the 'classic Rcpp API' was written during 2005 and 2006 by Dominick Samperi. This code has been factored out of Rcpp into the package RcppClassic, and it is still available for code relying on the older interface. New development should always use this Rcpp package instead.