C++ vs. Dart vs. R

C++ compiles directly to a machine's native code, allowing it to be one of the fastest languages in the world, if optimized.

Dart is a cohesive, scalable platform for building apps that run on the web (where you can use Polymer) or on servers (such as with Google Cloud Platform). Use the Dart language, libraries, and tools to write anything from simple scripts to full-featured apps.

R provides a wide variety of statistical (linear and nonlinear modelling, classical statistical tests, time-series analysis, classification, clustering, ...) and graphical techniques, and is highly extensible.