Algebraic expression in tree form with algorithm for finding best matching tree for given file with tuple: x - arg, y - arg, result.
For example Given
x y f(x,y)
2.4 3.5 18.2
4.0 -2.7 9.3
.
.
.
11.3 9.3 21.45
for that given input, using genetic programming, program is going to try to match best function (tree representation) that satisfies the given data.