% Specification of the railroad crossing example from M. Kanovich, M. Okada,
% and A. Scedrov, "Specifying Real-Time Finite-State Systems in Linear Logic".
% Forward chaining.
% Date: 7 July  1998
% Author: Iliano Cervesato

Forward chaining:

+ direct transcription of the specifications
+ efficient (the given rules favors forward chaining) (11 GC in the example)

- final values are hidden (unless we instrument the main routine with
  variables to get them; this can however be done systematically)

Performance (measured in number of calls to the GC)
* success (1,2,3,4) : 7 (avg)
* failure (1,1,1,4) : 5 (avg)