As proof of concept, we have applied our system to a symbolic regression problem used by Koza [Koza 92]. The system is given a set of input and output pairs, and must determine the function that maps one onto the other. The particular function Koza examined is X^{4} + X^{3} + X^{2} + Xwith the input values in the range [1..+1]. Table 4 contains a tableau which summarizes his experiments.

The production rules for <expr> are given above. As this and subsequent rules are the only ones that require a choice, they are the ones that will be evolved.
We adopt a similar style to Koza of summarizing information, using a modified version of his tableau. Notice how our terminal operands and terminal operators are analgous to GPTerminals and GPfunctions respectively.
