[p4bl0]

Actually if you had to do this kind of thing in C or any other non-homoiconic language, the right way to go would be to define data structures that represent your mathematical functions, and manipulate these structures to compute the derivatives (by pattern matching of the represented mathematical expression, exactly as you would do in Lisp using Lisp code which kind of is its own AST). And you would have to embed an interpreter for the mathematical expressions encoded in the data structures of your program, so you can not only manipulate the expressions, but also use them (which also comes for free in Lisp).

See Greenspun's tenth rule of programming.

[weland]

> Actually if you had to do this kind of thing in C or any other non-homoiconic language, the right way to go would be to define data structures that represent your mathematical functions, and manipulate these structures to compute the derivatives (by pattern matching of the represented mathematical expression, exactly as you would do in Lisp using Lisp code which kind of is its own AST).

Yes, of course. The language, being non-homoiconic, would require you to translate between a data representation that you can process and the data representation that the runtime can process.

However, if you were to do the equivalent thing -- that is, obtain the derivative based on the data representation that your runtime can process -- you'd have to examine the contents of the program memory itself. Needless to say, that would make things even unportable, or outright impossible due to compiler optimizations. But it would be the same thing :).

Edit: perversity bonus, you're working on a computer that does bank switching and the code that is computing the derivative is in a different memory bank than the function whose derivative it must compute.