Solidity Basic Solidity (Web Dev) 4

Question 1

What does 'assert()' do differently from 'require()' in Solidity?

Accepted Answer

assert() consumes all remaining gas on failure; require() refunds unused gas

Answer

assert() consumes all remaining gas and is for invariant checks; require() refunds gas and is for preconditions.

Question 2

In Solidity, what is 'abi.encode()' primarily used for?

Accepted Answer

ABI-encoding values into bytes for cross-contract calls or hashing

Answer

abi.encode() serializes values into ABI-encoded bytes, commonly used for hashing or low-level calls.

Question 3

Which modifier prevents a function from being re-entered before it finishes execution?

Accepted Answer

nonReentrant

Answer

The nonReentrant modifier (typically from OpenZeppelin's ReentrancyGuard) blocks recursive external calls.

Question 4

What does 'keccak256(abi.encodePacked(a, b))' compute in Solidity?

Accepted Answer

The Keccak-256 hash of the tightly packed encoding of a and b

Answer

keccak256 computes the Keccak-256 hash, and encodePacked tightly packs the inputs without padding.

Question 5

What is the maximum number of indexed parameters an event can have in Solidity?

Accepted Answer

3

Answer

Solidity events support up to 3 indexed parameters, which are stored as topics in the transaction log.

Solidity Practice Test