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Merge pull request #316 from chriseth/docs

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Fixes in the misc section.
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chriseth 2015-12-21 17:37:08 +01:00
commit 6b711d0527
2 changed files with 44 additions and 40 deletions
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4
docs/contracts.rst
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@ -124,6 +124,8 @@ This means that cyclic creation dependencies are impossible.
.. index:: ! visibility, external, public, private, internal
.. _visibility-and-accessors:
************************
Visibility and Accessors
************************
@ -232,6 +234,8 @@ is no good way to provide the key for the mapping.
.. index:: ! function;modifier
.. _modifiers:
******************
Function Modifiers
******************

80
docs/miscellaneous.rst
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@ -115,13 +115,13 @@ If `solc` is called with the option `--link`, all input files are interpreted to
Tips and Tricks
***************
* Use `delete` on arrays to delete all its elements.
* Use shorter types for struct elements and sort them such that short types are grouped together. This can lower the gas costs as multiple SSTORE operations might be combined into a single (SSTORE costs 5000 or 20000 gas, so this is what you want to optimise). Use the gas price estimator (with optimiser enabled) to check!
* Make your state variables public - the compiler will create [getters](#accessor-functions) for you for free.
* If you end up checking conditions on input or state a lot at the beginning of your functions, try using [modifiers](#function-modifiers)
* If your contract has a function called `send` but you want to use the built-in send-function, use `address(contractVariable).send(amount)`.
* If you want your contracts to receive ether when called via `send`, you have to implement the [fallback function](#fallback-functions).
* Initialise storage structs with a single assignment: `x = MyStruct({a: 1, b: 2});`
* Use `delete` on arrays to delete all its elements.
* Use shorter types for struct elements and sort them such that short types are grouped together. This can lower the gas costs as multiple SSTORE operations might be combined into a single (SSTORE costs 5000 or 20000 gas, so this is what you want to optimise). Use the gas price estimator (with optimiser enabled) to check!
* Make your state variables public - the compiler will create :ref:`getters <visibility-and-accessors>` for you for free.
* If you end up checking conditions on input or state a lot at the beginning of your functions, try using :ref:`modifiers`.
* If your contract has a function called `send` but you want to use the built-in send-function, use `address(contractVariable).send(amount)`.
* If you do **not** want your contracts to receive ether when called via `send`, you can add a throwing fallback function `function() { throw; }`.
* Initialise storage structs with a single assignment: `x = MyStruct({a: 1, b: 2});`
********
Pitfalls
@ -129,7 +129,7 @@ Pitfalls
Unfortunately, there are some subtleties the compiler does not yet warn you about.
- In `for (var i = 0; i < arrayName.length; i++) { ... }`, the type of `i` will be `uint8`, because this is the smallest type that is required to hold the value `0`. If the array has more than 255 elements, the loop will not terminate.
- In `for (var i = 0; i < arrayName.length; i++) { ... }`, the type of `i` will be `uint8`, because this is the smallest type that is required to hold the value `0`. If the array has more than 255 elements, the loop will not terminate.
**********
Cheatsheet
@ -140,30 +140,30 @@ Cheatsheet
Global Variables
================
- `block.coinbase` (`address`): current block miner's address
- `block.difficulty` (`uint`): current block difficulty
- `block.gaslimit` (`uint`): current block gaslimit
- `block.number` (`uint`): current block number
- `block.blockhash` (`function(uint) returns (bytes32)`): hash of the given block - only works for 256 most recent blocks
- `block.timestamp` (`uint`): current block timestamp
- `msg.data` (`bytes`): complete calldata
- `msg.gas` (`uint`): remaining gas
- `msg.sender` (`address`): sender of the message (current call)
- `msg.value` (`uint`): number of wei sent with the message
- `now` (`uint`): current block timestamp (alias for `block.timestamp`)
- `tx.gasprice` (`uint`): gas price of the transaction
- `tx.origin` (`address`): sender of the transaction (full call chain)
- `sha3(...) returns (bytes32)`: compute the Ethereum-SHA3 hash of the (tightly packed) arguments
- `sha256(...) returns (bytes32)`: compute the SHA256 hash of the (tightly packed) arguments
- `ripemd160(...) returns (bytes20)`: compute RIPEMD of 256 the (tightly packed) arguments
- `ecrecover(bytes32, uint8, bytes32, bytes32) returns (address)`: recover public key from elliptic curve signature
- `addmod(uint x, uint y, uint k) returns (uint)`: compute `(x + y) % k` where the addition is performed with arbitrary precision and does not wrap around at `2**256`.
- `mulmod(uint x, uint y, uint k) returns (uint)`: compute `(x * y) % k` where the multiplication is performed with arbitrary precision and does not wrap around at `2**256`.
- `this` (current contract's type): the current contract, explicitly convertible to `address`
- `super`: the contract one level higher in the inheritance hierarchy
- `selfdestruct(address)`: destroy the current contract, sending its funds to the given address
- `<address>.balance`: balance of the address in Wei
- `<address>.send(uint256) returns (bool)`: send given amount of Wei to address, returns `false` on failure.
- `block.coinbase` (`address`): current block miner's address
- `block.difficulty` (`uint`): current block difficulty
- `block.gaslimit` (`uint`): current block gaslimit
- `block.number` (`uint`): current block number
- `block.blockhash` (`function(uint) returns (bytes32)`): hash of the given block - only works for 256 most recent blocks
- `block.timestamp` (`uint`): current block timestamp
- `msg.data` (`bytes`): complete calldata
- `msg.gas` (`uint`): remaining gas
- `msg.sender` (`address`): sender of the message (current call)
- `msg.value` (`uint`): number of wei sent with the message
- `now` (`uint`): current block timestamp (alias for `block.timestamp`)
- `tx.gasprice` (`uint`): gas price of the transaction
- `tx.origin` (`address`): sender of the transaction (full call chain)
- `sha3(...) returns (bytes32)`: compute the Ethereum-SHA3 hash of the (tightly packed) arguments
- `sha256(...) returns (bytes32)`: compute the SHA256 hash of the (tightly packed) arguments
- `ripemd160(...) returns (bytes20)`: compute RIPEMD of 256 the (tightly packed) arguments
- `ecrecover(bytes32, uint8, bytes32, bytes32) returns (address)`: recover public key from elliptic curve signature
- `addmod(uint x, uint y, uint k) returns (uint)`: compute `(x + y) % k` where the addition is performed with arbitrary precision and does not wrap around at `2**256`.
- `mulmod(uint x, uint y, uint k) returns (uint)`: compute `(x * y) % k` where the multiplication is performed with arbitrary precision and does not wrap around at `2**256`.
- `this` (current contract's type): the current contract, explicitly convertible to `address`
- `super`: the contract one level higher in the inheritance hierarchy
- `selfdestruct(address)`: destroy the current contract, sending its funds to the given address
- `<address>.balance`: balance of the address in Wei
- `<address>.send(uint256) returns (bool)`: send given amount of Wei to address, returns `false` on failure.
.. index:: visibility, public, private, external, internal
@ -176,10 +176,10 @@ Function Visibility Specifiers
return true;
}
- `public`: visible externally and internally (creates accessor function for storage/state variables)
- `private`: only visible in the current contract
- `external`: only visible externally (only for functions) - i.e. can only be message-called (via `this.fun`)
- `internal`: only visible internally
- `public`: visible externally and internally (creates accessor function for storage/state variables)
- `private`: only visible in the current contract
- `external`: only visible externally (only for functions) - i.e. can only be message-called (via `this.fun`)
- `internal`: only visible internally
.. index:: modifiers, constant, anonymous, indexed
@ -187,8 +187,8 @@ Function Visibility Specifiers
Modifiers
=========
- `constant` for state variables: Disallows assignment (except initialisation), does not occupy storage slot.
- `constant` for functions: Disallows modification of state - this is not enforced yet.
- `anonymous` for events: Does not store event signature as topic.
- `indexed` for event parameters: Stores the parameter as topic.
- `constant` for state variables: Disallows assignment (except initialisation), does not occupy storage slot.
- `constant` for functions: Disallows modification of state - this is not enforced yet.
- `anonymous` for events: Does not store event signature as topic.
- `indexed` for event parameters: Stores the parameter as topic.