Common Lisp programs run by default in a way that calls to undefined functions are detected.
Here the Lisp simply tries to look up the function object from the symbol. There is no function, so it signals a condition (aka exception). The default exception handler gets called (without unwinding the stack). This handler prints the restarts and calls another REPL. I define the function -> the symbol now has a function definition. We then resume and Lisp tries again to get the function definition. The computation continues where we were.
That's the DEFAULT behavior you'll find in Common Lisp implementations.
Here the Lisp simply tries to look up the function object from the symbol. There is no function, so it signals a condition (aka exception). The default exception handler gets called (without unwinding the stack). This handler prints the restarts and calls another REPL. I define the function -> the symbol now has a function definition. We then resume and Lisp tries again to get the function definition. The computation continues where we were.
That's the DEFAULT behavior you'll find in Common Lisp implementations.