Added lottery.bas Smart Contract example.

lottery.bas

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+/* Lotter Smart Contract in DVM-BASIC  
+   This lottery smart contract  will give lottery wins every  xth try.
+*/
+
+
+
+        Function Lottery(value Uint64) Uint64
+	10  dim deposit_count,winner as Uint64
+	20  LET deposit_count =  LOAD("deposit_count")+1
+	25  IF value == 0 THEN GOTO 110  // if deposit amount is 0, simply return
+	30  STORE("depositor_address" + (deposit_count-1), SIGNER()) // store address for later on payment
+	40  STORE("deposit_total", LOAD("deposit_total") + value )
+	50  STORE("deposit_count",deposit_count)
+	60  IF LOAD("lotteryeveryXdeposit") > deposit_count THEN GOTO 110 // we will wait till X players join in
+	  // we are here means all players have joined in, roll the DICE, 
+	70  LET winner  = RANDOM() % deposit_count // we have a winner
+	80  SEND_DERO_TO_ADDRESS(LOAD("depositor_address" + winner) , LOAD("lotterygiveback")*LOAD("deposit_total")/10000)
+	
+            // re initialize for another round
+        90   STORE("deposit_count", 0)   //  initial players
+	100  STORE("deposit_total", 0)   //  total deposit of all players
+	110  RETURN 0
+	End Function
+
+	
+	// this function is used to initialize parameters during install time
+	Function Initialize() Uint64
+	10  STORE("owner", SIGNER())   // store in DB  ["owner"] = address
+	20  STORE("lotteryeveryXdeposit", 2)   // lottery will reward every X deposits
+        // how much will lottery giveback in 1/10000 parts, granularity .01 %
+	30  STORE("lotterygiveback", 9900)   // lottery will give reward 99% of deposits, 1 % is accumulated for owner to withdraw
+	33  STORE("deposit_count", 0)   //  initial players
+	34  STORE("deposit_total", 0)   //  total deposit of all players
+	35 printf "Initialize executed"
+	40 RETURN 0 
+	End Function 
+	
+	
+	
+        // used to tune lottery parameters
+	Function TuneLotteryParameters(input Uint64, lotteryeveryXdeposit Uint64, lotterygiveback Uint64) Uint64
+	10  dim key,stored_owner as String
+	20  dim value_uint64 as Uint64
+	30  IF ADDRESS_RAW(LOAD("owner")) == ADDRESS_RAW(SIGNER()) THEN GOTO 100  // check whether owner is real owner
+	40  RETURN 1
+	
+	100  STORE("lotteryeveryXdeposit", lotteryeveryXdeposit)   // lottery will reward every X deposits
+	130  STORE("lotterygiveback", value_uint64)   // how much will lottery giveback in 1/10000 parts, granularity .01 %
+	140  RETURN 0 // return success
+	End Function
+	
+
+	
+	// this function is used to change owner 
+	// owner is an string form of address 
+	Function TransferOwnership(newowner String) Uint64 
+	10  IF ADDRESS_RAW(LOAD("owner")) == ADDRESS_RAW(SIGNER()) THEN GOTO 30 
+	20  RETURN 1
+	30  STORE("tmpowner",newowner)
+	40  RETURN 0
+	End Function
+	
+	// until the new owner claims ownership, existing owner remains owner
+        Function ClaimOwnership() Uint64 
+	10  IF ADDRESS_RAW(LOAD("tmpowner")) == ADDRESS_RAW(SIGNER()) THEN GOTO 30 
+	20  RETURN 1
+	30  STORE("owner",SIGNER()) // ownership claim successful
+	40  RETURN 0
+	End Function
+	
+	// if signer is owner, withdraw any requested funds
+	// if everthing is okay, thety will be showing in signers wallet
+        Function Withdraw( amount Uint64) Uint64 
+	10  IF ADDRESS_RAW(LOAD("owner")) == ADDRESS_RAW(SIGNER()) THEN GOTO 30 
+	20  RETURN 1
+	30  SEND_DERO_TO_ADDRESS(SIGNER(),amount)
+	40  RETURN 0
+	End Function
+	
+	
+	
+
+