For Ruby pry comes close but he's right about the inability to have the same kind of turnaround cycle when you're developing a C extension. I don't think anyone

For Ruby pry comes close but he's right about the inability to have the same kind of turnaround cycle when you're developing a C extension. I don't think anyone is gonna beat SBCL in that regard any time soon. There is no way to take Ruby and then generate machine code that ends up being callable from the current address space. Although I guess there is some way to do it with cffi and a compiler constantly running in the background.