-- Solutions to exercises from the Central European Functional Programming summer school
-- July 4th-16th 2005

-- Write a Hume program to implement an or-gate;

-- HW-Hume solution
-- Note 
--   a) the use of boxes to generate test inputs/outputs;
--   b) the deliberate stopping of testb1 using (*,*); and
--   c) the automatic conversion from  Bit to string in the output of "or"

-- Kevin Hammond, 5th July 2005

program

 type Bit = int 1;

 box testb1
 in (n :: int 32) out (n' :: int 32, b :: Bit)
 match
   n -> if n > 3 then (*,*) else (n+1,if n < 2 then 0 else 1);

 box testb2
 in (b :: Bit) out (b1, b2 :: Bit)
 match
   0 -> (1,1)
 | 1 -> (0,0);

 box or
 in (b1,b2::Bit)
 out (s::Bit)
 match
    (0,0) -> 0
  | (_,_) -> 1;

 stream stdout to "std_err";

 wire testb1 (testb1.n') (testb1.n initially 0,or.b1);
 wire testb2 (testb2.b1) (testb2.b initially 1,or.b2);
 wire or (testb1.b,testb2.b2) (stdout);