ethers-rs/examples/big-numbers/README.md

# Big numbers
Ethereum uses big numbers (also known as "bignums" or "arbitrary-precision integers") to represent certain values in its codebase and in blockchain transactions. This is necessary because [the EVM](https://ethereum.org/en/developers/docs/evm) operates on a 256-bit word size, which is different from the usual 32-bit or 64-bit of modern machines. This was chosen for the ease of use with 256-bit cryptography (such as Keccak-256 hashes or secp256k1 signatures).

It is worth noting that Ethereum is not the only blockchain or cryptocurrency that uses big numbers. Many other blockchains and cryptocurrencies also use big numbers to represent values in their respective systems.

## Utilities
In order to create an application, it is often necessary to convert between the representation of values that is easily understood by humans (such as ether) and the machine-readable form that is used by contracts and math functions (such as wei). This is particularly important when working with Ethereum, as certain values, such as balances and gas prices, must be expressed in wei when sending transactions, even if they are displayed to the user in a different format, such as ether or gwei. To help with this conversion, ethers-rs provides two functions, `parse_units` and `format_units`, which allow you to easily convert between human-readable and machine-readable forms of values. `parse_units` can be used to convert a string representing a value in ether, such as "1.1", into a big number in wei, which can be used in contracts and math functions. `format_units` can be used to convert a big number value into a human-readable string, which is useful for displaying values to users.
refactor: examples (#1940) * ToC * Big numbers section * Middleware examples: builder * Middleware examples: gas_escalator * Middleware examples: gas_oracle * Middleware examples: signer * Middleware examples: missing stubs * review: applied DaniPopes suggestions to big numbers * typo * Middleware examples: nonce_manager * cargo +nightly fmt * update roadmap * Middleware examples: policy * Middleware examples: added docs * Contracts examples: created folder; included abigen example * Contracts examples: refactor abigen docs. Fixed cargo example reference * Contracts examples: contract_events; minor docs changes * Moved each example under its own crate. Cargo builds locally TODO: Fix broken examples CI * Big numbers examples: used regular operators for math * Single examples run correctly (missing overall CI execution) Example crates dependencies Removed duplicates * review: Applied gakonst note to remove commented items in workspace manifest * review: Applied gakonst note to restore visibility on contract constructor * ci: - Run/Build examples in a single step to avoid duplicated scripts - Removed ci.yaml step "Build all examples" * cargo +nightly fmt * ci: fix WASM step error * Removed deprecated EthGasStation example * WASM example uses local copy of `contract_abi.json`. In this way we keep the WASM example auto-consistent, at the cost of a small duplication * Cargo.lock aligned to master branch * Removed useless comments in examples * review: Applied gakonst note to add panic!() on the policy middleware example * review: Applied gakonst suggestion to add a custom middleware example * typos in docs * Update examples/big-numbers/examples/bn_math_operations.rs review: Accepted commit suggested by DaniPopes Co-authored-by: DaniPopes <57450786+DaniPopes@users.noreply.github.com> * review: Applied DaniPopes suggestion on assert_eq! * Update examples/big-numbers/README.md review: Accepted DaniPopes suggestion on big-numbers docs Co-authored-by: DaniPopes <57450786+DaniPopes@users.noreply.github.com> * review: All imports now reference the "ethers" crate * ci: added features ["ws", "rustls"] where needed cargo +nigthly fmt * Examples with special features (e.g. ipc, trezor etc.) are built alongside them. This is expressed as a "default" requirement in their respective Cargo.toml * cargo +nightly fmt * Examples: Gas oracle API keys from env Added missing features in middleware Cargo.toml * typo: use expect() instead of unwrap() * Updated ToC Moved 2 examples under more relevant folders * Gas oracle examples raise panic on middleware errors * review: removed useless [[example]] in Cargo.toml * review: removed #[allow(unused_must_use)] from gas_escalator example * review: Removed prefixes from file names * review: removed useless [[example]] in Cargo.toml * docs: Updated description to run examples in the workspace README.md Co-authored-by: Andrea Simeoni <> Co-authored-by: DaniPopes <57450786+DaniPopes@users.noreply.github.com> 2022-12-29 12:53:11 +00:00			`# Big numbers`
			`Ethereum uses big numbers (also known as "bignums" or "arbitrary-precision integers") to represent certain values in its codebase and in blockchain transactions. This is necessary because [the EVM](https://ethereum.org/en/developers/docs/evm) operates on a 256-bit word size, which is different from the usual 32-bit or 64-bit of modern machines. This was chosen for the ease of use with 256-bit cryptography (such as Keccak-256 hashes or secp256k1 signatures).`

			`It is worth noting that Ethereum is not the only blockchain or cryptocurrency that uses big numbers. Many other blockchains and cryptocurrencies also use big numbers to represent values in their respective systems.`

			`## Utilities`
			In order to create an application, it is often necessary to convert between the representation of values that is easily understood by humans (such as ether) and the machine-readable form that is used by contracts and math functions (such as wei). This is particularly important when working with Ethereum, as certain values, such as balances and gas prices, must be expressed in wei when sending transactions, even if they are displayed to the user in a different format, such as ether or gwei. To help with this conversion, ethers-rs provides two functions, `parse_units` and `format_units`, which allow you to easily convert between human-readable and machine-readable forms of values. `parse_units` can be used to convert a string representing a value in ether, such as "1.1", into a big number in wei, which can be used in contracts and math functions. `format_units` can be used to convert a big number value into a human-readable string, which is useful for displaying values to users.