Read about a REPL allowing to test things rapidly in C++:

Cling Aims to Provide a High-performance C++ REPL

by Sergio De Simone

From the article:

Cling is an interactive C++ interpreter that is built on top of LLVM and Clang and promises to provide a leap in productivity by going beyond the usual code-compile-run-debug C++ workflow...

Other useful materials:

• A short introduction video (youtube link)
• An article about C++ and scripting