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Understanding Algorand's smart contract language
- 1. Understanding Algorand’s Smart Contract Language
- 2. ● Agenda ○ Overview of the types of smart contracts ■ Stateless Contracts ■ Stateful Contracts ■ Combining with other Algorand Technologies ○ Runtime Architecture ■ Stateless ■ Stateful ○ TEAL - Algorand Smart Contract Language ■ Opcodes and Examples ○ PyTeal and Reach Algorand Smart Contracts
- 3. Algorand Smart Contracts - Layer 1 Smart Contract Contract or Escrow Delegation Application Stateless Stateful
- 4. Escrow/Contract Account Stateless Smart Contract - Compiled Logic Becomes an Account Standard/Multisig Account Standard/Multisig Account Standard/Multisig Account Fund Account With Standard Transactions Assets/Algos Spend Transactions Gated by TEAL Program Standard/Multisig Account TEAL Logic
- 5. Delegate Stateless Smart Contract - Logic Standard/Multisig Account Spend Transactions Gated by TEAL Program Standard/Multisig Account TEAL Logic Standard Transaction Sign Transaction Sign TEAL Logic Later Logic Signature
- 6. Stateless Contract Usages • Contract Accounts • Escrows • HTLC • Split Payments • Limit Orders • Delegated • Recurring Payments • Limited Account Authority
- 7. Stateful aka Apps Application Transaction Smart Contract Logic Global State Local State User 1 Local State User 1 Local State User 1 Local State User 1 Approval Program Clear Program Smart Contract Logic Deployed Stateful Contract Returns APPID Communicate with Application Transactions
- 8. New Transaction Sub-Types for Application NoOp TEAL Logic Modify Local or Global state TEAL Logic Modify Local or Global state Approval Program Clear Program Optin DeleteApplication UpdateApplication CloseOut Clear Used to Communicate With Stateful Smart Contract Graceful Non-Graceful ie Will clear regardless
- 9. Stateful Contract Usages • Defi Apps (AMM, lending, etc) • Crowdfunding • Voting • Material Tracking • Lottery • Seating • Identity Restrictions • Anywhere a global variable is needed • Anywhere a individual users values need to be manipulated
- 10. Stateful vs Stateless Differences Stateful Stateless Evaluation Block Assembly Submission Size 1kb 1000 bytes Opcodes 700/Program 20000 Access to Ledger Facilitates Assets/Account Lookups Only Tx Based Values Track State Values Yes No Logic Lives on Chain Submitted with Tx(s) Templates Not Currently Yes (HTLC, Split, etc)
- 12. CrowdFunding App Donation Operation Stateful Contract App Global State Fund Start Date Fund End Date Fund Goal Fund Amount Escrow Address Creator Address Receiver Address Fund Close Date Stateless Contract Escrow Holds All Donations Donate Transaction 2 - Payment Tx From Donator to Escrow Account Transaction 1 Stateful App Transaction Atomic Local Storage Giving Amount
- 13. Voting App - Vote Operation Spend Vote Token Receive Vote Token From Commission Global State Registration Begin Round Registration End Round Vote Begin Round Vote End Round Candidate A Votes Candidate B Votes Vote Creator Stateful Contract App Transaction 2 - Asset Xfer From Voter to Commision Account Transaction 1 Stateful App Transaction Atomic Vote Commission
- 15. Stack Runtime Stateless Runtime Architecture Global Vars Transaction(s) Properties Read Only Temporary Scratch Read/Write TEAL Program Arguments Per Transaction Transaction Submission
- 16. Teal Stack Architecture (Stateless) #pragma version 3 txn Receiver addr SOEI... == && arg 0 len int 32 == && arg 0 sha256 byte base64 VeU... == && ... Program uint64/[]byte uint64/[]byte uint64/[]byte Stack …(up to 1000) 0: uint64/[]byte 1: uint64/[]byte 2: uint64/[]byte Scratch Space ... 255: uint64/[]byte 0: []byte 1: []byte 2: []byte Args (This txn only) …(up to 255) ● Sender ● Fee ● FirstValid ● FirstValidTime ● LastValid ● Note ● Lease ● Receiver ● Amount ● CloseRemainderTo ● VotePK ● SelectionPK ● VoteFirst ● VoteLast ● VoteKeyDilution ● Type ● TypeEnum ● XferAsset ● AssetAmount ● AssetSender ● AssetReceiver ● AssetCloseTo ● GroupIndex ● TxID Transaction(s)
- 17. Stateful Contract Runtime Stateful Runtime Architecture Global Vars Transaction(s) Properties Read Only Stack TEAL Program(s), Loaded on Create Update Application Array - limit 2 Arguments Array Per Transaction Transaction Submission Accounts Array - limit 4 Temporary Scratch Read/Write Global/Local State Assets Array - limit 2
- 18. Teal Stack Architecture (Stateful) #pragma version 3 byte "myarg" txn ApplicationArgs 0 == bz no_local int 0 byte "test" app_local_get pop no_local: // read global state byte "counter" app_global_get ... Program uint64/[]byte uint64/[]byte uint64/[]byte Stack …(up to 1000) 0: uint64/[]byte 1: uint64/[]byte 2: uint64/[]byte Scratch Space ... 255: uint64/[]byte Transaction(s) []byte []byte []byte Arguments* …(up to 16 & 2K) uint64 uint64 Applications* …(up to 2 app ids) []byte []byte Accounts* …(up to 4 accounts) Global State 64 K/V pairs 64 bytes Local State 16 K/V pairs 64 bytes * Can change per transaction ● Sender ● Fee ● FirstValid ● FirstValidTime ● LastValid ● Note ● Lease ● Receiver ● Amount ● CloseRemainderTo ● VotePK ● SelectionPK ● VoteFirst ● VoteLast ● VoteKeyDilution ● Type ● TypeEnum ● XferAsset ● AssetAmount ● AssetSender ● AssetReceiver ● AssetCloseTo ● GroupIndex ● TxID uint64 uint64 Assets* …(up to 2 asset ids)
- 19. TEAL
- 20. TEAL - Transaction Execution Approval Language ● Bytecode based stack language ● Returns True or False (One Positive Value Left on Stack) ● SDK Support ● > 80 Opcodes ● Access to ASA/Algo Balances ● Read all Transactions in a Group ● Stateful - Global/Local Storage Calls ● Stateless - Signature Verification ● PyTEAL library to write in python Push Pop
- 21. Simple Stack Example txn Amount int 1000 >= Transaction Amount txn Amount int 1000 >= 1 1000 Transaction Amount txn Amount int 1000 >= 2 txn Amount int 1000 >= T r a n s a c t i o n A m o u n t 3 1 0 0 0 0/1 Transaction Amount >= 1000
- 23. Pseudo Operators int //load an int onto stack byte //Load bytes on stack addr //Load Algorand address TEAL Approval Program txn Receiver addr HJLWACXDBOEH25KJB2WI2X5BHQOJ4LS2MRLNMHJ5ZZOBLJU7KGDJSHEU3I == . byte “mystring” txn ApplicationArgs 0 ==
- 24. State Demo
- 25. Branching Demo - b, bnz, bz
- 26. Accessing Transaction Properties TEAL Approval Program txn Amount int 1000 >= ● Sender ● Fee ● FirstValid ● FirstValidTime ● LastValid ● Note ● Lease ● Receiver ● Amount ● CloseRemainderTo ● VotePK ● SelectionPK ● VoteFirst ● VoteLast ● VoteKeyDilution ● Type ● TypeEnum ● XferAsset ● AssetAmount ● AssetSender ● AssetReceiver ● AssetCloseTo ● GroupIndex ● TxID
- 27. Global Variables
- 28. Checking Type of Transaction TEAL Approval Program txn TypeEnum int appl ==
- 29. Application Transaction Sub-Types - Stateful TEAL Approval Program txn OnCompletion int NoOp ==
- 30. Atomic Transactions - gtxn vs txn Transaction 1 Call to Stateful Contract Transaction 2 Payment Transaction Transaction 3 Asset Transfer Transaction Atomic TEAL Approval Program global GroupSize int 3 == gtxn 0 TypeEnum int appl == && gtxn 1 TypeEnum Int pay == && gtxn 2 TypeEnum axfer == &&
- 31. Atomic Demo
- 32. Asset Check TEAL Approval Program int 0 //Sender of tx int 2 //asset id asset_holding_get AssetBalance pop //assume they have the asset int 1 >= Transaction 1 Call to Stateful Contract
- 33. Read Global State From Another Contract Readonly
- 34. Read Other Contracts State Demo
- 35. Reading and Writing Local State int 0 //sender byte "MyAmountGiven" txn Amount app_local_put int 0 //sender byte "MyAmountGiven" app_local_get int 1 //Account 1 int 1234 //other contract id byte “OtherContractKey” app_local_get_ex Account 1 Account 2 Accounts Transaction 1 Call to Stateful Contract Account 3 Account 4 Sender Local State 16 K/V pairs 64 bytes Account 1 Local State 16 K/V pairs 64 bytes Local State 16 K/V pairs 64 bytes Account 4 Read/Write Read Only Account 4 Local State 16 K/V pairs 64 bytes for Different Contract Local State 16 K/V pairs 64 bytes for Different Contract Sender
- 36. Escrow Demo
- 38. Smart Contract Options TEAL PyTeal Compiler Reach Application Business Logic TEAL TEAL TEAL TEAL
- 39. def bank_for_account(receiver): is_payment = Txn.type_enum() == TxnType.Payment is_single_tx = Global.group_size() == Int(1) is_correct_receiver = Txn.receiver() == Addr(receiver) return And( is_payment, is_single_tx, is_correct_receiver ) if __name__ == "__main__": program = bank_for_account("ZZAF5ARA4MEC5PVDOP64JM5O5MQST63Q2KOY2FLYFL XXD3PFSNJJBYAFZM") print(compileTeal(program, Mode.Signature)) PyTEAL -Python Library Returns #pragma version 2 txn TypeEnum int pay == global GroupSize int 1 == && txn Receiver addr ZZAF5ARA4MEC5PVDOP64JM5O5MQST63Q2KOY2FLYFLXXD3P FSNJJBYAFZM == &&
- 41. Reach - Reach.sh
- 43. Follow Guidelines for Safety Boilerplate Approval Program Example Stateless Contract Adhere to These Guidelines to Protect Accounts Size Limitations and Opcode Cost Limits
- 45. Resources ● Discord: https://discord.gg/YgPTCVk ● Developer Portal (Documentation and Tutorials): https://developer.algorand.org/ ● Forum: https://forum.algorand.org/ ● GitHub: https://github.com/algorand ● OFFICE HOURS sign up: https://www.algorand.com/developers