Pure Function

Pronunciation

[pyoor fungk-shun]

Analogy

A pure function is like a mathematical function f(x)=x²—it always returns the same output for the same input without side effects.

Definition

A function modifier indicating the function neither reads nor writes contract , depending only on its input parameters.

Key Points Intro

Pure functions guarantee referential via:

Key Points

No state access: Disallows `SLOAD` and `SSTORE`.

No global variables: Cannot read `msg.*` or block data.

Deterministic: Same inputs always yield same outputs.

Gas-free off‑chain: Callable without gas via `eth_call`.

Example

``` function add(uint256 a, uint256 b) external pure returns (uint256) { return a + b; } ```

Technical Deep Dive

The compiler enforces no opcodes that access or environment. Pure functions are optimized aggressively, inlined when possible. marks them as `pure` in `stateMutability`.

Security Warning

Complex pure functions can still run out of when used in transactions; keep logic simple.

Caveat

Cannot interact with on‑chain data or other contracts.

Related Terms

Blockchain & Cryptocurrency Glossary

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