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Diffstat (limited to 'docs')
| -rw-r--r-- | docs/contracts.rst | 36 | ||||
| -rw-r--r-- | docs/contracts/constant-state-variables.rst | 35 |
2 files changed, 36 insertions, 35 deletions
diff --git a/docs/contracts.rst b/docs/contracts.rst index 746f6e00..c9adb03b 100644 --- a/docs/contracts.rst +++ b/docs/contracts.rst @@ -441,41 +441,7 @@ all symbols visible from the function are visible in the modifier. Symbols introduced in the modifier are not visible in the function (as they might change by overriding). -.. index:: ! constant - -************************ -Constant State Variables -************************ - -State variables can be declared as ``constant``. In this case, they have to be -assigned from an expression which is a constant at compile time. Any expression -that accesses storage, blockchain data (e.g. ``now``, ``address(this).balance`` or -``block.number``) or -execution data (``msg.value`` or ``gasleft()``) or makes calls to external contracts is disallowed. Expressions -that might have a side-effect on memory allocation are allowed, but those that -might have a side-effect on other memory objects are not. The built-in functions -``keccak256``, ``sha256``, ``ripemd160``, ``ecrecover``, ``addmod`` and ``mulmod`` -are allowed (even though, with the exception of ``keccak256``, they do call external contracts). - -The reason behind allowing side-effects on the memory allocator is that it -should be possible to construct complex objects like e.g. lookup-tables. -This feature is not yet fully usable. - -The compiler does not reserve a storage slot for these variables, and every occurrence is -replaced by the respective constant expression (which might be computed to a single value by the optimizer). - -Not all types for constants are implemented at this time. The only supported types are -value types and strings. - -:: - - pragma solidity >=0.4.0 <0.6.0; - - contract C { - uint constant x = 32**22 + 8; - string constant text = "abc"; - bytes32 constant myHash = keccak256("abc"); - } +.. include:: contracts/constant-state-variables.rst .. index:: ! functions diff --git a/docs/contracts/constant-state-variables.rst b/docs/contracts/constant-state-variables.rst new file mode 100644 index 00000000..3e615ed0 --- /dev/null +++ b/docs/contracts/constant-state-variables.rst @@ -0,0 +1,35 @@ +.. index:: ! constant + +************************ +Constant State Variables +************************ + +State variables can be declared as ``constant``. In this case, they have to be +assigned from an expression which is a constant at compile time. Any expression +that accesses storage, blockchain data (e.g. ``now``, ``address(this).balance`` or +``block.number``) or +execution data (``msg.value`` or ``gasleft()``) or makes calls to external contracts is disallowed. Expressions +that might have a side-effect on memory allocation are allowed, but those that +might have a side-effect on other memory objects are not. The built-in functions +``keccak256``, ``sha256``, ``ripemd160``, ``ecrecover``, ``addmod`` and ``mulmod`` +are allowed (even though, with the exception of ``keccak256``, they do call external contracts). + +The reason behind allowing side-effects on the memory allocator is that it +should be possible to construct complex objects like e.g. lookup-tables. +This feature is not yet fully usable. + +The compiler does not reserve a storage slot for these variables, and every occurrence is +replaced by the respective constant expression (which might be computed to a single value by the optimizer). + +Not all types for constants are implemented at this time. The only supported types are +value types and strings. + +:: + + pragma solidity >=0.4.0 <0.6.0; + + contract C { + uint constant x = 32**22 + 8; + string constant text = "abc"; + bytes32 constant myHash = keccak256("abc"); + } |