slides_e.tex

数据挖掘中de一个算法 hamster的实例

\documentstyle[german,a4]{article}
\pagestyle{empty}
\advance\topmargin-15mm
\textwidth190mm
\textheight250mm
\advance\oddsidemargin-25mm

\begin{document}
\Large

\begin{verbatim}
------------------------------------------------------------------------
-- Hamster Methods
------------------------------------------------------------------------

-- enquiries --
get_x:    INTEGER               -- get hamster x-position
get_y:    INTEGER               -- get hamster y-position
get_dir:  INTEGER               -- get hamster direction
get_look: INTEGER               -- get outlook in current direction
get_corn: INTEGER               -- get amount of corn on field
get_load: INTEGER               -- get amount of corn in cheeks

-- actions --
move:     INTEGER               -- move hamster forward
turn (t:      INTEGER)          -- turn hamster 90 degrees
take (amount: INTEGER): INTEGER -- take some corn
drop (amount: INTEGER): INTEGER -- drop some corn





------------------------------------------------------------------------
-- Hamster Control Function
------------------------------------------------------------------------

class CONTROL
inherit CLIENT
  redefine control
end
creation
  make

feature
control (hamster: HAMSTER) is
do
  ...
end  -- control
\end{verbatim}

\newpage
\begin{verbatim}
------------------------------------------------------------------------
-- Constants
------------------------------------------------------------------------

max_x:      INTEGER is  64;     -- maximal x-extension of maze
max_y:      INTEGER is  64;     -- maximal y-extension of maze
max_corn:   INTEGER is 255;     -- maximal size of corn heap
max_load:   INTEGER is  12;     -- maximal load of corn in cheeks

-- results of get_dir
east:       INTEGER is   0;     -- hamster is looking east
north:      INTEGER is   1;     -- hamster is looking north
west:       INTEGER is   2;     -- hamster is looking west
south:      INTEGER is   3;     -- hamster is looking south

-- results of get_look
empty:      INTEGER is   0;     -- there is an empty field ahead
corn:       INTEGER is   1;     -- there is a field with corn ahead
wall:       INTEGER is   2;     -- there is a wall ahead

-- parameters of turn
pos:        INTEGER is   1;     -- positive turn (counterclockwise)
neg:        INTEGER is  -1;     -- negative turn (clockwise)
left:       INTEGER is   1;     -- left     turn (counterclockwise)
right:      INTEGER is  -1;     -- right    turn (clockwise)
\end{verbatim}

\newpage
\begin{verbatim}
------------------------------------------------------------------------
-- Example Hamster Control Function
------------------------------------------------------------------------

control (hamster: HAMSTER) is   -- hamster control function (random)
local
  movecnt: INTEGER;             -- number of moves made
  turn   : INTEGER;             -- turn direction (left/right)
  d      : INTEGER;             -- dummy variable for results
do
  from
    movecnt := 0;               -- initialize the move counter
  until
    movecnt = 50                -- make 50 field to field moves
  loop
    if     hamster.get_x = 0    -- if we are at home (initial position),
    and    hamster.get_y = 0    -- drop all the corn we have
    then   d := hamster.drop(hamster.max_load);
    elseif hamster.get_corn > 0 -- if there is corn on the field
    then   d := hamster.take(hamster.max_load);
    end                         -- take as much as he can carry
    if hamster.get_look = hamster.wall  -- if the way is blocked
    or else random(4) <= 1      -- or just because it's funny (25%)
    then if random(2) <= 1      -- randomly choose a turn direction
         then turn := hamster.left;
         else turn := hamster.right;
         end                    -- (50% either way)
         from
           hamster.turn(turn);  -- turn the hamster
         until                  -- in the chosen direction
           hamster.get_look /= hamster.wall
         loop                   -- repeat turning the hamster around
           hamster.turn(turn);  -- until no wall blocks the way
         end
    end
    d := hamster.move;          -- move the hamster forward
    movecnt := movecnt +1;      -- and count the move made
  end
end  -- control
\end{verbatim}

\end{document}