InvX: An automatic function inverter. We have implemented InvX, a system that will mechanically generate inverses for a substantial class of functions. By applying an extended set of function-level axioms at compile-time, expressions for the inverses are transformed so that no unification is required at run-time in many cases. This makes the cost of their execution comparable with that of reduction-based semantics. We have also described the incorporation of InvX in the FLAGSHIP programming environment. InvX has been used successfully on a wide range of examples.