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Merge pull request #5854 from ethereum/docs-string-man-fix

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[DOCS] fix string manipulation innacuracies
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Alex Beregszaszi 2019-02-05 16:01:56 +00:00 committed by GitHub
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docs/types/reference-types.rst
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@ -106,7 +106,7 @@ Array elements can be of any type, including mapping or struct. The general
restrictions for types apply, in that mappings can only be stored in the restrictions for types apply, in that mappings can only be stored in the
``storage`` data location and publicly-visible functions need parameters that are :ref:`ABI types <ABI>`. ``storage`` data location and publicly-visible functions need parameters that are :ref:`ABI types <ABI>`.
It is possible to mark arrays ``public`` and have Solidity create a :ref:`getter <visibility-and-getters>`. It is possible to mark state variable arrays ``public`` and have Solidity create a :ref:`getter <visibility-and-getters>`.
The numeric index becomes a required parameter for the getter. The numeric index becomes a required parameter for the getter.
Accessing an array past its end causes a failing assertion. You can use the ``.push()`` method to append a new element at the end or assign to the ``.length`` :ref:`member <array-members>` to change the size (see below for caveats). Accessing an array past its end causes a failing assertion. You can use the ``.push()`` method to append a new element at the end or assign to the ``.length`` :ref:`member <array-members>` to change the size (see below for caveats).
@ -119,10 +119,9 @@ Variables of type ``bytes`` and ``string`` are special arrays. A ``bytes`` is si
but it is packed tightly in calldata and memory. ``string`` is equal to ``bytes`` but does not allow but it is packed tightly in calldata and memory. ``string`` is equal to ``bytes`` but does not allow
length or index access. length or index access.
While Solidity does not have string manipulation functions, you can use Solidity does not have string manipulation functions, but there are
this implicit conversion for equivalent functionality. For example to compare third-party string libraries. You can also compare two strings by their keccak256-hash using
two strings ``keccak256(abi.encode(s1)) == keccak256(abi.encode(s2))``, or to ``keccak256(abi.encodePacked(s1)) == keccak256(abi.encodePacked(s2))`` and concatenate two strings using ``abi.encodePacked(s1, s2)``.
concatenate two strings already encoded with ``abi.encodePacked(s1, s2);``.
You should use ``bytes`` over ``byte[]`` because it is cheaper, since ``byte[]`` adds 31 padding bytes between the elements. As a general rule, You should use ``bytes`` over ``byte[]`` because it is cheaper, since ``byte[]`` adds 31 padding bytes between the elements. As a general rule,
use ``bytes`` for arbitrary-length raw byte data and ``string`` for arbitrary-length use ``bytes`` for arbitrary-length raw byte data and ``string`` for arbitrary-length