lang/m2/test/Thalmann/Shoes.mod

   1 MODULE Shoes;
   2
   3 (* From: MODULA-2, An Introduction, by Daniel Thalmann, Springer-Verlag,
   4          New York, 1985
   5    Figure 21.3
   6 *)
   7
   8   FROM SYSTEM IMPORT WORD, ADR, ADDRESS, NEWPROCESS, TRANSFER;
   9   FROM InOut IMPORT Write, WriteLn;
  10
  11   CONST
  12         WorkLength = 200;
  13         MaxShoes = 50;
  14         MaxDif = 6;
  15
  16   TYPE
  17         WorkSpace = ARRAY [0..WorkLength-1] OF WORD;
  18
  19   VAR
  20         NbLeft, NbRight : INTEGER;
  21         WSLeft, WSRight : WorkSpace;
  22         Left, Right, Main : ADDRESS;
  23
  24   PROCEDURE Leftp;
  25   BEGIN
  26         WHILE NbLeft < MaxShoes DO
  27                 INC(NbLeft);
  28                 Write("L");
  29                 IF (NbLeft-NbRight>=MaxDif) OR (NbLeft>=MaxShoes) THEN
  30                         TRANSFER(Left,Right);
  31                 END;
  32         END;
  33         WriteLn;
  34   END Leftp;
  35
  36   PROCEDURE Rightp;
  37   BEGIN
  38         WHILE NbRight < MaxShoes DO
  39                 INC(NbRight);
  40                 Write("R");
  41                 IF (NbRight-NbLeft>=MaxDif) OR (NbRight>=MaxShoes) THEN
  42                         TRANSFER(Right,Left);
  43                 END;
  44         END;
  45         WriteLn;
  46   END Rightp;
  47
  48 BEGIN
  49         NbLeft := 0;
  50         NbRight := 0;
  51         NEWPROCESS(Leftp,ADR(WSLeft),SIZE(WSLeft),Left);
  52         NEWPROCESS(Rightp,ADR(WSRight),SIZE(WSRight),Right);
  53         TRANSFER(Main,Left);
  54 END Shoes.