Example of Lottery Smart Contract in DVM-BASIC.
Guide on how to run Dero Smart Contract
/* Lottery 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
```