You keep saying "without an interpreter" but
Does anyone know of a function that will take some string as a parameter and convert it to live code?
is a fairly workable definition of 'interpreter', and you certainly can't execute code without at some point 'interpreting' its meaning, can you?
If your aim is simply to get inline execution working, consider the Visual Studio mechanism of handing it off to the compiler and executing it asynchronously from the GUI components of the program.
I do something similar in vim (albeit synchronously) by mapping C-F5 to run C++ code:
map <C-F5> :w !g++ -x c++ -Wall -Wextra -o ~/.vimrun - && ~/.vimrun<CR>
One problem with this approach is linking... normal C++ code needs some linker directives and possibly a specific include path. Visual Studio uses the project configuration to add "references" (IIRC) that are linked during the inline compile stage, and I just add my libraries to the macro directly since I generally work with the same small group of tools.
If you wanted to automatically enable API access you'd have to either link with everything by default (probably a bad idea) or do your own pre-processing with a large database of supported APIs, looking for things like #include <boost/filesystem/operations.hpp> to map to -lboost_filesystem in the compiler switches.