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Diffstat (limited to 'docs/units-and-global-variables.rst')
| -rw-r--r-- | docs/units-and-global-variables.rst | 78 |
1 files changed, 39 insertions, 39 deletions
diff --git a/docs/units-and-global-variables.rst b/docs/units-and-global-variables.rst index 8fa515cc..8f910c80 100644 --- a/docs/units-and-global-variables.rst +++ b/docs/units-and-global-variables.rst @@ -7,23 +7,23 @@ Units and Globally Available Variables Ether Units =========== -A literal number can take a suffix of :code:`wei`, :code:`finney`, :code:`szabo` or :code:`ether` to convert between the subdenominations of Ether, where Ether currency numbers without a postfix are assumed to be "wei", e.g. :code:`2 ether == 2000 finney` evaluates to :code:`true`. +A literal number can take a suffix of ``wei``, ``finney``, ``szabo`` or ``ether`` to convert between the subdenominations of Ether, where Ether currency numbers without a postfix are assumed to be "wei", e.g. ``2 ether == 2000 finney`` evaluates to ``true``. .. index:: time, seconds, minutes, hours, days, weeks, years Time Units ========== -Suffixes of :code:`seconds`, :code:`minutes`, :code:`hours`, :code:`days`, :code:`weeks` and +Suffixes of ``seconds``, ``minutes``, ``hours``, ``days``, ``weeks`` and `years` after literal numbers can be used to convert between units of time where seconds are the base unit and units are considered naively in the following way: - * :code:`1 == 1 second` - * :code:`1 minutes == 60 seconds` - * :code:`1 hours == 60 minutes` - * :code:`1 days == 24 hours` - * :code:`1 weeks = 7 days` - * :code:`1 years = 365 days` + * ``1 == 1 second`` + * ``1 minutes == 60 seconds`` + * ``1 hours == 60 minutes`` + * ``1 days == 24 hours`` + * ``1 weeks = 7 days`` + * ``1 years = 365 days`` Take care if you perform calendar calculations using these units, because not every year equals 365 days and not even every day has 24 hours @@ -50,29 +50,29 @@ namespace and are mainly used to provide information about the blockchain. Block and Transaction Properties ------------------------------------ - - :code:`block.coinbase` (:code:`address`): current block miner's address - - :code:`block.difficulty` (:code:`uint`): current block difficulty - - :code:`block.gaslimit` (:code:`uint`): current block gaslimit - - :code:`block.number` (:code:`uint`): current block number - - :code:`block.blockhash` (:code:`function(uint) returns (bytes32)`): hash of the given block - only for 256 most recent blocks - - :code:`block.timestamp` (:code:`uint`): current block timestamp - - :code:`msg.data` (:code:`bytes`): complete calldata - - :code:`msg.gas` (:code:`uint`): remaining gas - - :code:`msg.sender` (:code:`address`): sender of the message (current call) - - :code:`msg.sig` (:code:`bytes4`): first four bytes of the calldata (i.e. function identifier) - - :code:`msg.value` (:code:`uint`): number of wei sent with the message - - :code:`now` (:code:`uint`): current block timestamp (alias for :code:`block.timestamp`) - - :code:`tx.gasprice` (:code:`uint`): gas price of the transaction - - :code:`tx.origin` (:code:`address`): sender of the transaction (full call chain) + - ``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 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.sig`` (``bytes4``): first four bytes of the calldata (i.e. function identifier) + - ``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) .. note:: - The values of all members of :code:`msg`, including :code:`msg.sender` and - :code:`msg.value` can change for every **external** function call. + The values of all members of ``msg``, including ``msg.sender`` and + ``msg.value`` can change for every **external** function call. This includes calls to library functions. If you want to implement access restrictions in library functions using - :code:`msg.sender`, you have to manually supply the value of - :code:`msg.sender` as an argument. + ``msg.sender``, you have to manually supply the value of + ``msg.sender`` as an argument. .. note:: The block hashes are not available for all blocks for scalability reasons. @@ -84,17 +84,17 @@ Block and Transaction Properties Mathematical and Cryptographic Functions ---------------------------------------- -:code:`addmod(uint x, uint y, uint k) returns (uint)`: - compute :code:`(x + y) % k` where the addition is performed with arbitrary precision and does not wrap around at :code:`2**256`. -:code:`mulmod(uint x, uint y, uint k) returns (uint)`: - compute :code:`(x * y) % k` where the multiplication is performed with arbitrary precision and does not wrap around at :code:`2**256`. -:code:`sha3(...) returns (bytes32)`: +``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``. +``sha3(...) returns (bytes32)``: compute the Ethereum-SHA-3 hash of the (tightly packed) arguments -:code:`sha256(...) returns (bytes32)`: +``sha256(...) returns (bytes32)``: compute the SHA-256 hash of the (tightly packed) arguments -:code:`ripemd160(...) returns (bytes20)`: +``ripemd160(...) returns (bytes20)``: compute RIPEMD-160 hash of the (tightly packed) arguments -:code:`ecrecover(bytes32 data, uint8 v, bytes32 r, bytes32 s) returns (address)`: +``ecrecover(bytes32 data, uint8 v, bytes32 r, bytes32 s) returns (address)``: recover the address associated with the public key from elliptic curve signature In the above, "tightly packed" means that the arguments are concatenated without padding. @@ -106,20 +106,20 @@ This means that the following are all identical:: sha3(6382179) sha3(97, 98, 99) -If padding is needed, explicit type conversions can be used: :code:`sha3("\x00\x12")` is the -same as :code:`sha3(uint16(0x12))`. +If padding is needed, explicit type conversions can be used: ``sha3("\x00\x12")`` is the +same as ``sha3(uint16(0x12))``. -It might be that you run into Out-of-Gas for :code:`sha256`, :code:`ripemd160` or :code:`ecrecover` on a *private blockchain*. The reason for this is that those are implemented as so-called precompiled contracts and these contracts only really exist after they received the first message (although their contract code is hardcoded). Messages to non-existing contracts are more expensive and thus the execution runs into an Out-of-Gas error. A workaround for this problem is to first send e.g. 1 Wei to each of the contracts before you use them in your actual contracts. This is not an issue on the official or test net. +It might be that you run into Out-of-Gas for ``sha256``, ``ripemd160`` or ``ecrecover`` on a *private blockchain*. The reason for this is that those are implemented as so-called precompiled contracts and these contracts only really exist after they received the first message (although their contract code is hardcoded). Messages to non-existing contracts are more expensive and thus the execution runs into an Out-of-Gas error. A workaround for this problem is to first send e.g. 1 Wei to each of the contracts before you use them in your actual contracts. This is not an issue on the official or test net. .. index:: this, selfdestruct Contract Related ---------------- -:code:`this` (current contract's type): +``this`` (current contract's type): the current contract, explicitly convertible to :ref:`address` -:code:`selfdestruct(address)`: +``selfdestruct(address)``: destroy the current contract, sending its funds to the given :ref:`address` Furthermore, all functions of the current contract are callable directly including the current function. |