Simple Markov chain simulation by external call to random() C function :

- random.epi : Heptagon interface containing the declaration of
  random() function

- random.h, random.c : "glue" between actual random() C function and
  function calls generated by Heptagon

- markov.ept : contains node "process", simulating a two-state Markov
  chain, with probability p (constant) at each step to go from one
  state to the other

Function "random" and node "process" are declared unsafe to avoid
optimization removing calls to "random" ("random" has side effects).

Compilation and simulation :

heptc random.epi
heptc -target c -s process -hepts markov.ept
gcc -I . -I markov_c -I /usr/local/lib/heptagon/c random.c markov_c/_main.c markov_c/markov.c markov_c/markov_types.c -o markov
hepts -mod Markov -node process -exec ./markov