1. A method of block diagram modeling in a data processing system, comprising: in a first block, receiving a first value indicative of an index into a lookup table; in the first block, generating information indicative of the location of the first value relative to a predefined domain of possible indexed values that define regions; in a second block, receiving the information generated by the first block; and using the information received in the second block to determine an output value of a first lookup table.