Programming language for self-modifying code?

Question

• I am recently thinking about writing self-modifying programs, I think it may be powerful and fun. So I am currently looking for a language that allows

Answer 1

You can do this in Maple (the computer algebra language). Unlike those many answers above which use compiled languages which only allow you to create and link in new code at run-time, here you can honest-to-goodness modify the code of a currently-running program. (Ruby and Lisp, as indicated by other answerers, also allow you to do this; probably Smalltalk too).

Actually, it used to be standard in Maple that most library functions were small stubs which would load their 'real' self from disk on first call, and then self-modify themselves to the loaded version. This is no longer the case as the library loading has been virtualized.

As others have indicated: you need an interpreted language with strong reflection and reification facilities to achieve this.

I have written an automated normalizer/simplifier for Maple code, which I proceeded to run on the whole library (including itself); and because I was not too careful in all of my code, the normalizer did modify itself. I also wrote a Partial Evaluator (recently accepted by SCP) called MapleMIX - available on sourceforge - but could not quite apply it fully to itself (that wasn't the design goal).