A new characterization of Mehlhorn´s polynomial time functionals

A. Cobham (1964) presented a machine-independent characterization of computational feasibility, via inductive definition. R. Constable (1973) was apparently the first to consider the notion of feasibility for type 2 functionals. K. Mehlhorn´s (1976) study of feasible reducibilities proceeds from Constable´s work. Here, a class of polytime operators is defined, using a generalization of Cobham´s definition. The authors provide an affirmative answer to the question of whether there is a natural machine based definition of Mehlhorn´s class