-- rational numbers class in Eiffel

class RATIONAL

creation make  -- "creation means constructor"

feature { RATIONAL } -- list of classes "features" are visible to
                   -- {ANY} is same as public (same as Object in java)
                   -- {NONE} is stronger than private
                   -- {RATIONAL} same as private in Java/C++

num: integer;      -- int num;
dem: integer;

feature { RATIONAL, RATS }

make(n:integer; d:integer) is   -- constructor  
  require d > 0    -- raise exception otherwise
  do
    num := n;      -- assignment is :=, equality is =
    dem := d;
  end; -- make

invert is          -- void invert(void) ...
  local 
     temp: integer;
  do
    temp := num;
    num := dem;
    dem := temp;
  end;

rateq(other: RATIONAL) : boolean is   -- boolean rateq(RATIONAL other)
 do
   result := (num*other.dem) = (dem*other.num);  -- result is keyword
 end;
  

printrat is 
 do
   io.put_integer(num);
   io.put_string("/");
   io.put_integer(dem);
 end;

end -- class RATIONAL