Cling is described as 'interactive C++ interpreter, built on the top of LLVM and Clang libraries. Its advantages over the standard interpreters are that it has command line prompt and uses just-in-time (JIT) compiler for compilation' and is an app in the Development category. There are three alternatives to Cling for Linux, BSD, Mac and Windows. The best alternative is Ch, which is free. Other great apps like Cling are Interactive GCC (IGCC) (Free, Open Source) and CINT (Free, Open Source).
Ch is a C/C++ interpreter and scripting language environment used by teachers, students, engineers and scientists around the world to learn math, numerical computing, C/C++, and write cross-platform code and embedded scripts quickly and efficiently.
IGCC is a real-eval-print loop (REPL) simulator for C/C++ programmers. It allows you to type C++ commands which are immediately compiled and executed. Underneath it uses the normal GCC exe for compiling.
CINT is an interpreter for C and C++ code. It is useful e.g. for situations where rapid development is more important than execution time. Using an interpreter the compile and link cycle is dramatically reduced facilitating rapid development.