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Text Adventure Demo using Finite State Machine

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    Text Adventure Demo using Finite State Machine

    This example really pushes the envelope and does things that are frowned on within certain circles.
    It is posted here to show some of the Power available with the new PowerObjects. It would be of interest to anyone creating text based adventure games and those who want to learn how to implement FMS's(see below) with PowerBasic 5/9.
    Note to [email protected]. I have permission from the author to use his code. I will forward the email if requested.
    I am not seasoned OOP programmer by any means but this code seems stable.

    James


    Back ground:
    I started investigating FSM's (Finite State Machines) as they are used in RPG game development and came across a number of interesting articles. The one that really caught my eye was an exert from a book written by Mat Buckland (url in the code). By using his methods outlined you eliminate the monster if / then | select / case normally used in these games. He writes of course in C++ and it took some magic to finally come up with a way to implement in PBCC 5.
    '******************************************************************************
    Problem:
    There is no documented way to pass an OBJECTPTR to a Function/Sub/Method AS A BYVAL DWORD.
    ******************************************************************************
    Magic Part #1
    Example:
    This does not work:
    Code:
    METHOD M1(BYVAL MyobjPtr AS DWORD) 
   LOCAL oMyObj AS iMyObj
   oMyObj = MyObjPtr
    You would need to this:
    Code:
    METHOD M1(BYVAL Myobj AS iMyObj ) 
   LOCAL oMyObj AS iMyObj
   oMyObj = MyObj
    But what if we really need to pass a DWORD
    Here is how this is done but be very careful
    Code:
    METHOD M1(BYVAL MyobjPtr AS DWORD) 
   LOCAL oMyObj AS iMyObj
   POKE DWORD,VARPTR(oMyObj),MyObjPtr)
   IF ISNOTHING(oMyObj) THEN EXIT METHOD
   oMyObj.AddRef
    Explanation:

    The MyObjPtr is an iMyObj Object created outside the METHOD
    There is no assignment for oMyObj (we poke it). When the METHOD Ends
    it is noted by the compiler that the oMyObj variable contains a valid object reference
    so it Calls the COM Release Method to deallocate all the internal stuff.
    woops we just NOTHING'ed our original passed in OBJECT so off to GPF land.

    To counteract this we use the (PB undocumented - although well known COM call) AddRef
    oMyObj.AddRef

    Magic Part #2.
    I needed a way to fool the compiler into thinking it was dealing with just one type of
    Class/Interface while in reality there were as many different class/interface as there
    were locations.
    Solution:
    I use what is called in C++ as a Virtual Class. It has no functionality and is used strictly
    as a base class shown below
    Code:
    CLASS cState
    INTERFACE iState : INHERIT IUNKNOWN
        METHOD Enter(BYVAL Agent AS tAgent)
        END METHOD
        METHOD Execute(BYVAL Agent AS tAgent)
        END METHOD
        METHOD EXIT(BYVAL Agent AS tAgent)
        END METHOD
    END INTERFACE
END CLASS
    All Location classes inherit from this class. They then flesh out the three methods Enter,

    Execute, Exit.

    We have two Control states Called oNewState, oCurrentState also derived from cState/iState.
    We then use the same method describe abouve to POKE the OBJPTR's of the locations to oNewState

    Code:
    'SED_PBCC
'******************************************************************************
'               A Finite State Machine example written in PBCC 5.0
'                                James C. Fuller
'                                August 11,2008
'                             jcf[email protected]
'
'******************************************************************************
'==============================================================================
'Based on WestWorld c++ example by  Mat Buckland 2002 ([email protected])
'------------------------------------------------------------------------------
'##############################################################################
'If you are unfamilar with FSM's here are a few links:
'******************************************************************************
' This one is where I got the code my example is based.
' http://www.ai-junkie.com/architecture/state_driven/tut_state1.html
'******************************************************************************
'------------------------------------------------------------------------------
' http://aigamedev.com/questions/fsm-implementation
'------------------------------------------------------------------------------
'http://klabs.org/DEI/References/design_guidelines/nasa_guidelines/fsm/finite_state_machines.htm
'------------------------------------------------------------------------------
'http://www.rwc.uc.edu/koehler/comath/34.html
'------------------------------------------------------------------------------
'http://centipedia.com/articles/Finite_state_automaton
'------------------------------------------------------------------------------
'http://www.aiwisdom.com/bytopic_statemachines.html
'##############################################################################
'I'll try to explain how this works.
'I use a completely Virtual Base Class (cState/iState) that is inherited by all
'the State Classes so I can fool the Update Method into thinking it's dealing
'with a single class. We don't have Pointers that can be used and instantiated so
' this approach seems to work fine?
'##############################################################################
'Each location is a class composed of three state classes(Enter,Execute,Exit)
' all inherited from cState/iState
'******************************************************************************
'Note TRACE is enabled specifically to check  for AddRef problems. The areas where
'it is used here should always print 2. The origianl and the one we add. When the
'local scope ends the compiler reduces the count by one; exactly what we want.

'******************************************************************************
#COMPILE EXE
#DIM ALL
%shack = 1
%goldmine = 2
%bank = 3
%saloon = 4
$AgentNames="Miner Bob;Elsa"
MACRO FUNCTION GetAgentName(Id)
END MACRO = PARSE$($AgentNames,";",Id)
MACRO MyTrace(MyStr)
	TRACE ON
	TRACE PRINT MyStr
	TRACE OFF
END MACRO
%AGENT_MINERBOB = 1
TYPE tAgent
	AgentObj	AS DWORD			'Holds OBJPTR(ME)
	AgentType	AS LONG
END TYPE
'==============================================================================
CLASS cBaseGameEntity
    INSTANCE m_id,m_NextValidId AS LONG
    INTERFACE iBaseGameEntiy :INHERIT IUNKNOWN
        PROPERTY GET m_id() AS LONG
            PROPERTY = m_id
        END PROPERTY
        PROPERTY SET m_id(BYVAL Param AS LONG)
             m_id = Param
        END PROPERTY
    END INTERFACE
END CLASS
'==============================================================================
CLASS cMiner
    INSTANCE Location,GoldCarried,MoneyInBank,Thirst,Fatigue AS LONG
    INSTANCE ComfortLevel,MaxNuggets,ThirstLevel,TirednessThreshold AS LONG
    INSTANCE oCurrentState AS iState
    INSTANCE oNewState AS iState
	INSTANCE oGoHomeAndSleepTilRested AS iGoHomeAndSleepTilRested
	INSTANCE Agent AS tAgent
'------------------------------------------------------------------------------
    CLASS METHOD CREATE
        ComfortLevel = 5
        MaxNuggets = 3
        ThirstLevel = 5
        TirednessThreshold = 5
        Location = %shack
		Agent.AgentType = %AGENT_MINERBOB
    END METHOD
'------------------------------------------------------------------------------
    INTERFACE iMiner : INHERIT cBaseGameEntity, iBaseGameEntiy
		PROPERTY GET Agent() AS tAgent
			PROPERTY = Agent
		END PROPERTY
        PROPERTY GET Location() AS LONG
            PROPERTY = Location
        END PROPERTY
'..............................................................................
        PROPERTY GET GoldCarried() AS LONG
            PROPERTY = GoldCarried
        END PROPERTY
        PROPERTY SET GoldCarried(BYVAL Param AS LONG)
            GoldCarried = Param
        END PROPERTY
        PROPERTY GET ComfortLevel() AS LONG
            PROPERTY = ComfortLevel
        END PROPERTY
        PROPERTY SET oNewState(BYVAL dwNewState AS DWORD)
		    POKE DWORD,VARPTR(oNewState),dwNewState
            oNewState.AddRef
        END PROPERTY
'..............................................................................
        METHOD ChangeLocation(BYVAL NewLocation AS LONG)
            Location = NewLocation
        END METHOD
'------------------------------------------------------------------------------
'This is where the states are changed
'------------------------------------------------------------------------------
        METHOD UpDate()AS LONG
			LOCAL RefC AS LONG ,TrStr AS STRING
            Thirst +=1
'This will be the first time UpDate is Called
' Create the Start Location -> oGoHomeAndSleepTilRested
			IF Agent.AgentObj = 0 THEN		'First Time
				Agent.AgentObj = OBJPTR(ME)
				oGoHomeAndSleepTilRested = CLASS "cGoHomeAndSleepTilRested"
'We can't just do an  assignment because they are not the same interface but
'we can do a little trick that works fine
				POKE DWORD,VARPTR(oNewState),OBJPTR(oGoHomeAndSleepTilRested)
'This is undocumented but works fine. just make sure either out of scope or = NOTHIMG's
'match the AddRef. For debugging you can check the Count which is returned from AddRef.
				RefC = oNewState.AddRef
				TrStr = "oNewState RefC in UpDate = " + FORMAT$(Refc)
			END IF
			IF ISOBJECT(oNewState) THEN
				'No oCurrentState if First Update
				IF ISOBJECT(oCurrentState) THEN
					oCurrentState.Exit(Agent)
					oCurrentState = NOTHING
				END IF
				oCurrentState = oNewState
				oNewState = NOTHING
				oCurrentState.Enter(Agent)

			END IF

            IF ISOBJECT(oCurrentState) THEN
                oCurrentState.Execute(Agent)
            END IF

        END METHOD
'------------------------------------------------------------------------------
        METHOD AddToGoldCarried(BYVAL Amount AS LONG)
            GoldCarried += Amount
        END METHOD
'------------------------------------------------------------------------------
        METHOD IncreaseFatigue()
            Fatigue += 1
        END METHOD
'------------------------------------------------------------------------------
        METHOD DecreaseFatigue()
            Fatigue -= 1
        END METHOD
'------------------------------------------------------------------------------
        METHOD PocketsFull() AS LONG
            METHOD = (GoldCarried >= MaxNuggets)
        END METHOD
'------------------------------------------------------------------------------
        METHOD Thirsty() AS LONG
            METHOD = (Thirst >= ThirstLevel)
        END METHOD
'------------------------------------------------------------------------------
        METHOD Wealth() AS LONG
            METHOD = MoneyInBank
        END METHOD
'------------------------------------------------------------------------------
        METHOD SetWealth(BYVAL Param AS LONG)
            MoneyInBank = Param
        END METHOD
'------------------------------------------------------------------------------
        METHOD AddToWealth(BYVAL Param AS LONG)
            MoneyInBank += Param
            IF MoneyInBank < 0 THEN
                MoneyInBank = 0
            END IF
        END METHOD
'------------------------------------------------------------------------------
        METHOD BuyAndDrinkAWhiskey()
            Thirst = 0
            MoneyInBank -= 2
        END METHOD
'------------------------------------------------------------------------------
        METHOD Fatigued() AS LONG
            METHOD = (Fatigue > TirednessThreshold)
        END METHOD
'------------------------------------------------------------------------------
    END INTERFACE
END CLASS
'=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
'Virtual State Class
'This is the Class/Interface that is the base for all Locations and in C++
'terms in is a Virtual Class with no functionality on it's own.
'=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
CLASS cState
    INTERFACE iState : INHERIT IUNKNOWN
        METHOD Enter(BYVAL Agent AS tAgent)
        END METHOD
        METHOD Execute(BYVAL Agent AS tAgent)
        END METHOD
        METHOD EXIT(BYVAL Agent AS tAgent)
        END METHOD
    END INTERFACE
END CLASS
'=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
CLASS cEnterMineAndDigForNugget
	INTERFACE iEnterMineAndDigForNugget : INHERIT cState,iState

'------------------------------------------------------------------------------
        OVERRIDE METHOD Enter(BYVAL Agent AS tAgent)
			LOCAL oMiner AS iMiner
			LOCAL RefC AS LONG ,TrStr AS STRING
			IF Agent.AgentType = %AGENT_MINERBOB THEN
				POKE DWORD,VARPTR(oMiner),Agent.AgentObj
				IF ISNOTHING(oMiner) THEN
					EXIT METHOD
				END IF
				RefC = oMiner.AddRef
				TrStr = "oMiner RefC in cEnterMineAndDigForNugget Enter = " + FORMAT$(RefC)
				MyTrace(TrStr)
				IF oMiner.Location <> %goldmine THEN
					PRINT GetAgentName(1); ": Walking to the Glodmine"
					oMiner.ChangeLocation(%goldmine)
				END IF
			'ELSEIF	Agent.AgentType = Something Else
			END IF
        END METHOD
'------------------------------------------------------------------------------
        OVERRIDE METHOD Execute(BYVAL Agent AS tAgent)
			LOCAL Id AS LONG
			LOCAL oMiner AS iMiner
			LOCAL oVisitBankAndDepositGold AS iVisitBankAndDepositGold
			LOCAL oQuenchThirst AS iQuenchThirst
			LOCAL RefC AS LONG ,TrStr AS STRING
			IF Agent.AgentType = %AGENT_MINERBOB THEN
				POKE DWORD,VARPTR(oMiner),Agent.AgentObj
				IF ISNOTHING(oMiner) THEN
					EXIT METHOD
				END IF
				ReFc=oMiner.AddRef
				TrStr = "oMiner RefC in cEnterMineAndDigForNugget Execute = " + FORMAT$(RefC)
				MyTrace(TrStr)

				Id = oMiner.m_id
				oMiner.AddToGoldCarried(1)
				oMiner.IncreaseFatigue()
				PRINT GetAgentName(Id); ": Picking Up a Nugget"
				IF oMiner.PocketsFull() THEN
					oVisitBankAndDepositGold = CLASS "cVisitBankAndDepositGold"
					IF ISNOTHING(oVisitBankAndDepositGold) THEN
						EXIT METHOD
					END IF
					oVisitBankAndDepositGold.AddRef
					oMiner.oNewState = OBJPTR(oVisitBankAndDepositGold)
					PRINT GetAgentName(Id); ": Pockets Full"
				END IF

				IF oMiner.Thirsty THEN
					oQuenchThirst = CLASS "cQuenchThirst"
					oQuenchThirst.Addref
					oMiner.oNewState = (OBJPTR(oQuenchThirst))
				END IF
			END IF
        END METHOD
'------------------------------------------------------------------------------
        OVERRIDE METHOD Exit(BYVAL Agent AS tAgent)
			LOCAL oMiner AS iMiner
			LOCAL Id AS LONG
			LOCAL RefC AS LONG,TrStr AS STRING
			IF Agent.AgentType = %AGENT_MINERBOB THEN
				POKE DWORD,VARPTR(oMiner),Agent.AgentObj
				Id = oMiner.m_id
				RefC=oMiner.AddRef
				TrStr = "oMiner RefC in cEnterMineAndDigForNugget Exit = " + FORMAT$(RefC)
				MyTrace(TrStr)

				PRINT GetAgentName(Id); ": Ah'm leavin' the goldmine with mah pockets full o' sweet gold"
			END IF
        END METHOD
    END INTERFACE
END CLASS
'******************************************************************************
CLASS cVisitBankAndDepositGold
    INSTANCE oGoHomeAndSleepTilRested AS iGoHomeAndSleepTilRested
    INSTANCE oEnterMineAndDigForNugget AS iEnterMineAndDigForNugget
	INSTANCE Id AS LONG
    INTERFACE iVisitBankAndDepositGold : INHERIT cState,iState
        OVERRIDE METHOD Enter(BYVAL Agent AS tAgent)
			LOCAL oMiner AS iMiner
			IF Agent.AgentType = %AGENT_MINERBOB THEN
				POKE DWORD,VARPTR(oMiner),Agent.AgentObj
				oMiner.AddRef
				IF oMiner.Location <> %Bank THEN
					PRINT GetAgentName(1); ": Walking to the Bank"
					oMiner.ChangeLocation(%Bank)
				END IF
			END IF
        END METHOD
'------------------------------------------------------------------------------
        OVERRIDE METHOD Execute(BYVAL Agent AS tAgent)
			LOCAL oMiner AS iMiner
            IF Agent.AgentType = %AGENT_MINERBOB THEN
				POKE DWORD,VARPTR(oMiner),Agent.AgentObj
				oMiner.AddRef
				oMiner.AddToWealth(oMiner.GoldCarried)
				oMiner.GoldCarried = 0
				PRINT GetAgentName(1); ": Depositing gold. Total savings now: ";oMiner.Wealth
				IF oMiner.Wealth >= oMiner.ComfortLevel THEN
					PRINT GetAgentName(1); ": WooHoo! Rich enough for now. Back home to mah li'lle lady"
					oGoHomeAndSleepTilRested = CLASS "cGoHomeAndSleepTilRested"
					oMiner.oNewState = OBJPTR(oGoHomeAndSleepTilRested)
				ELSE
					oEnterMineAndDigForNugget = CLASS "cEnterMineAndDigForNugget"
					oMiner.oNewState = OBJPTR(oEnterMineAndDigForNugget)
				END IF
			END IF
        END METHOD
'------------------------------------------------------------------------------
        OVERRIDE METHOD Exit(BYVAL Agent AS tAgent)
            PRINT GetAgentName(1); ": Leaving The Bank"
        END METHOD
'------------------------------------------------------------------------------
    END INTERFACE
END CLASS
'=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
CLASS cGoHomeAndSleepTilRested
	INSTANCE oEnterMineAndDigForNugget AS iEnterMineAndDigForNugget
	INSTANCE Id AS LONG
    INTERFACE iGoHomeAndSleepTilRested : INHERIT cState,iState
        OVERRIDE METHOD Enter(BYVAL Agent AS tAgent)
			LOCAL oMiner AS iMiner
            IF Agent.AgentType = %AGENT_MINERBOB THEN
				POKE DWORD,VARPTR(oMiner),Agent.AgentObj
				oMiner.AddRef
				IF oMiner.Location <> %Shack THEN
					PRINT GetAgentName(1); ": Walking to the Shack"
					oMiner.ChangeLocation(%Shack)
				END IF
			END IF
        END METHOD
'------------------------------------------------------------------------------
        OVERRIDE METHOD Execute(BYVAL Agent AS tAgent)
			LOCAL oMiner AS iMiner
            IF Agent.AgentType = %AGENT_MINERBOB THEN
				POKE DWORD,VARPTR(oMiner),Agent.AgentObj
				oMiner.AddRef
				IF ISFALSE(oMiner.Fatigued) THEN
					PRINT GetAgentName(1); ": What a Gol darn fantastic nap! Time to find more gold"
					oEnterMineAndDigForNugget = CLASS "cEnterMineAndDigForNugget"
					oMiner.oNewState = OBJPTR(oEnterMineAndDigForNugget)
				ELSE
					oMiner.DecreaseFatigue
					PRINT GetAgentName(1); ": ZZZZ....."
				END IF
			END IF
        END METHOD
'------------------------------------------------------------------------------
        OVERRIDE METHOD Exit(BYVAL Agent AS tAgent)
            PRINT GetAgentName(1); ": Leaving the House"
        END METHOD
'------------------------------------------------------------------------------
    END INTERFACE
END CLASS
'=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
CLASS cQuenchThirst
	INSTANCE oEnterMineAndDigForNugget AS iEnterMineAndDigForNugget
    INTERFACE iQuenchThirst : INHERIT cState,iState
        OVERRIDE METHOD Enter(BYVAL Agent AS tAgent)
			LOCAL oMiner AS iMiner
            IF Agent.AgentType = %AGENT_MINERBOB THEN
				POKE DWORD,VARPTR(oMiner),Agent.AgentObj
				oMiner.AddRef
				IF oMiner.Location <> %Saloon THEN
					oMiner.ChangeLocation(%Saloon)
					PRINT GetAgentName(1); ": Boy, ah sure is thusty! Walking to the saloon"
				END IF
			END IF
        END METHOD
'------------------------------------------------------------------------------
        OVERRIDE METHOD Execute(BYVAL Agent AS tAgent)
			LOCAL oMiner AS iMiner
            IF Agent.AgentType = %AGENT_MINERBOB THEN
				POKE DWORD,VARPTR(oMiner),Agent.AgentObj
				oMiner.AddRef
				IF oMiner.Thirsty THEN
					oMiner.BuyAndDrinkAWhiskey
					PRINT GetAgentName(1); ": That's mighty fine sippin liquer"
					oEnterMineAndDigForNugget = CLASS "cEnterMineAndDigForNugget"
					oMiner.oNewState =OBJPTR(oEnterMineAndDigForNugget)
				ELSE
					PRINT "Error"
					PRINT "Error"
					PRINT "Error"
				END IF
			END IF
        END METHOD
'------------------------------------------------------------------------------
        OVERRIDE METHOD Exit(BYVAL Agent AS tAgent)
            PRINT GetAgentName(1); ": Leaving the Saloon"
        END METHOD
    END INTERFACE
END CLASS
'=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
FUNCTION PBMAIN () AS LONG
    LOCAL oMiner AS iMiner
    LOCAL i AS LONG

TRACE NEW "WW15_TRACE.TXT"
    COLOR 11
    oMiner = CLASS "cMiner"
	oMiner.m_Id = 1
    FOR i = 1 TO 20
        IF oMiner.UpDate() < 0 THEN
            PRINT "Bad UpDate"
            EXIT FOR
        END IF
        Sleep 1000
    NEXT i

    PRINT "Any Key To Exit"

    WAITKEY$

TRACE CLOSE

END FUNCTION
    Attached Files
    Tags: None
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