We describe a method that permits the user of a mechanized mathematical logic to write
elegant logical definitions while allowing sound and efficient execution. In particular, the
features supporting this method allow the user to install, in a logically sound way, alternative
executable counterparts for logically defined functions. These alternatives are often much
more efficient than the logically equivalent terms they replace. These features have been
implemented in the ACL2 theorem prover, and we discuss several applications of the features
in ACL2.Ministerio de Educación y Ciencia TIN2004–0388
