Therefore, the whole approach works because Listable functions return the same list structure as their arguments and the order in which the elements are visited is the correct one. If f finally meets a list element, it returns the replacement element and the list structure is preserved. The important thing is, that f has the attribute Listable which makes that it is first distributed to all elements in the list, no matter how deeply they are nested. This procedure is straightforward but, after this, I want to select only the last 2 roots, and to store them as variables, say w1 and w2. Every time it is called with any argument, it returns the next element from the list l by using the counter i. Hello guys I want to solve a 4th order equation, and to find its solutions. The function f doesn't really do something. OK, to give some hints: Above we want to structure the list l exactly the same way as o. This can be prevented by using this shorter equivalent: unflatten := Module[ Or some other way in which the dependence of each function on the others is made explicit.As described here, the solution below leaks symbols in the global namespace.

Here is my first naive attempt to do this:

All the same, it is an elusive thing to pin down because different functions seem to have different requirements for such entities. I want this function to return these functions y and z as rules, much as NDSolve returns a rule for evaluating a function. Anecdote: Way back in the last millenium someone in the Kernel Dept scheduled a meeting to discuss the issue of 'What is a variable' This was within the setting of Mathematica, not general math or CS. Suppose that the solution to this differential equation defines some other functions y(t) and z(t).

I have written a small Mathematica package that contains a module that solves some differential equation with initial conditions.

Flatten mathematica