Examples: ERC20, ERC721, and ArbPrecompileProbe

This document describes three example contracts and their companion scripts:

• contracts/examples/ERC20.sol with scripts/examples/deploy-erc20.js
• contracts/examples/ERC721.sol with scripts/examples/deploy-erc721.js
• contracts/examples/ArbPrecompileProbe.sol with scripts/examples/arb-precompile-probe.js

The token examples demonstrate standard deployment and basic interactions. The precompile probe demonstrates reads against ArbSys (0x…64) and ArbGasInfo (0x…6c) in the local environment (shim mode or native if available).

Prerequisites (all examples)

• Hardhat project with @nomicfoundation/hardhat-ethers and the Arbitrum patch plugin configured.

• A local network:

  • Ephemeral: --network hardhat (default), or
  • Persistent: a running node such as npx hardhat node --port 8549 and networks.localhost configured in hardhat.config.js.

• For ArbPrecompileProbe:

  • Shims predeployed at the canonical precompile addresses or native handlers active.
  • Typical predeploy script: scripts/predeploy-precompiles.js.

ERC20 Example

Contract

File: contracts/examples/ERC20.sol A minimal ERC-20 with constructor parameters (name, symbol, initialSupply) and standard getters.

Script

File: scripts/examples/deploy-erc20.js Actions performed:

1. Deploy ERC20 with example parameters.
2. Read name, symbol, and totalSupply.
3. Transfer a small amount to another account and print the recipient balance.

Run

npx hardhat --config hardhat.config.js run --network localhost scripts/examples/deploy-erc20.js

Example output

ERC20 deployed: 0x5FbDB2315678afecb367f032d93F642f64180aa3
 name: Token
 symbol: TK
 totalSupply: 1000000000000000000000000
 transfer 100 → 0x70997970C51812dc3A010C7d01b50e0d17dc79C8
 recipient balance: 100000000000000000000

Notes

• Output values reflect constructor arguments and post-transfer state on the local network.
• No dependency on precompiles for this example.

ERC721 Example

Contract

File: contracts/examples/ERC721.sol A minimal ERC-721 with constructor parameters (name, symbol) and a simple mint(to, tokenId) function.

Script

File: scripts/examples/deploy-erc721.js Actions performed:

1. Deploy ERC721 with example parameters.
2. Mint tokenId = 1 to a second account.
3. Read ownerOf(1) and print the result.

Run

npx hardhat --config hardhat.config.js run --network localhost scripts/examples/deploy-erc721.js

Example output

ERC721 deployed: 0x9fE46736679d2D9a65F0992F2272dE9f3c7fa6e0
 name: NFT
 symbol: XNFT
 minted tokenId 1 to 0x70997970C51812dc3A010C7d01b50e0d17dc79C8
 ownerOf(tokenId): 0x70997970C51812dc3A010C7d01b50e0d17dc79C8

Notes

• Standard ERC-721 behavior on a local network.
• No dependency on precompiles for this example.

ArbPrecompileProbe Example

Contract

File: contracts/examples/ArbPrecompileProbe.sol Purpose: demonstrate EVM calls to Arbitrum precompiles from a contract on a local chain.

Interfaces:

• ArbSys at 0x0000000000000000000000000000000000000064
• ArbGasInfo at 0x000000000000000000000000000000000000006C (Uppercase checksum …006C is used in the Solidity literal to satisfy the compiler.)

Provided view functions (typical):

• probeChainId() → returns the chain ID through ArbSys.
• probeL1Estimate() → returns the L1 estimate through ArbGasInfo.getCurrentTxL1GasFees() (shim mode returns the seeded estimate deterministically).
• probeTuple() → returns the getPricesInWei() 6-tuple (shim order).

Script

File: scripts/examples/arb-precompile-probe.js Actions performed:

1. Deploy ArbPrecompileProbe.
2. Call probeChainId(), probeL1Estimate(), and probeTuple().
3. Print results.

Run

# If using shims, predeploy once to the persistent node:
npx hardhat --config hardhat.config.js run --network localhost scripts/predeploy-precompiles.js

# Then run the probe:
npx hardhat --config hardhat.config.js run --network localhost scripts/examples/arb-precompile-probe.js

Example output

ArbPrecompileProbe deployed: 0xa513E6E4b8f2a923D98304ec87F64353C4D5C853
probeChainId(): 42161
probeL1Estimate(): 1000000000
probeTuple(): [ '69440', '1000000000', '2000000000000', '100000000', '0', '100000000' ]

Notes

• Values reflect the current state of the local environment:

  • Shim mode: values mirror the last seeded tuple and chain ID.
  • Native mode (if enabled in other phases): values reflect the handler’s logic.

• Reseeding ArbGasInfoShim via arb:reseed-shims immediately affects probeL1Estimate() and probeTuple() on subsequent calls.

Reference Table

Common commands

# Persistent local node
npx hardhat node --port 8549

# Predeploy shims (if using shim mode for the probe)
npx hardhat --config hardhat.config.js run --network localhost scripts/predeploy-precompiles.js

# Deploy ERC20 and perform a transfer
npx hardhat --config hardhat.config.js run --network localhost scripts/examples/deploy-erc20.js

# Deploy ERC721 and mint tokenId 1
npx hardhat --config hardhat.config.js run --network localhost scripts/examples/deploy-erc721.js

# Probe Arbitrum precompiles
npx hardhat --config hardhat.config.js run --network localhost scripts/examples/arb-precompile-probe.js

Expected outcomes (summary)

• ERC20 example confirms standard ERC-20 deployment and transfer on the local chain.
• ERC721 example confirms standard ERC-721 deployment, minting, and ownership on the local chain.
• ArbPrecompileProbe confirms functional reads from ArbSys and ArbGasInfo in the local environment, making precompile-dependent logic demonstrable and testable with deterministic shim data.