Header-Only 'C++' and 'R' Interface R package cpp4r version 1.1.0 Provides a header only, 'C++' interface to 'R' with enhancements over 'cpp11'. Enforces copy-on-write semantics consistent with 'R' behavior. Offers native support for ALTREP objects, 'UTF-8' string handling, modern 'C++' features and idioms, and reduced memory requirements. Allows for vendoring, making it useful for restricted environments. Compared to 'cpp11', it adds support for converting 'C++' maps to 'R' lists, 'Roxygen' documentation directly in 'C++' code, proper handling of matrix attributes, support for nullable external pointers, bidirectional copy of complex number types, flexibility in type conversions, use of nullable pointers, and various performance optimizations. Software Depends: R (>= 4.0.0) Suggests: roxygen2, tinytest Mauricio Vargas Sepulveda <m.vargas.sepulveda@gmail.com> Comprehensive R Archive Network (CRAN) Mauricio Vargas Sepulveda [aut, cre] (ORCID: <https://orcid.org/0000-0003-1017-7574>), Posit Software, PBC [aut] (Original cpp11 package) Apache License (>= 2) 2026-07-21 application/tgz https://CRAN.R-project.org/package=cpp4r doi:10.32614/CRAN.package.cpp4r