replaced case expressions with multi-equation function definitions over algebraic types, including natural numbers, e.g. fib (0) <= 1 fib (1) <= 1 fib (n+2)
Oxford University Press, 2005, ISBN 0-19-856746-4 Giulini, Domenico, Algebraic and Geometric Structures in Special Relativity, Ehlers, Jürgen; Lämmerzahl