[DOCS] Final updates to types section.

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chriseth 2018-09-20 14:00:01 +02:00
parent 2150aea344
commit cb7866916e

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@ -1050,11 +1050,13 @@ If ``a`` is an LValue (i.e. a variable or something that can be assigned to), th
delete delete
------ ------
``delete a`` assigns the initial value for the type to ``a``. I.e. for integers it is equivalent to ``a = 0``, but it can also be used on arrays, where it assigns a dynamic array of length zero or a static array of the same length with all elements reset. For structs, it assigns a struct with all members reset. ``delete a`` assigns the initial value for the type to ``a``. I.e. for integers it is equivalent to ``a = 0``, but it can also be used on arrays, where it assigns a dynamic array of length zero or a static array of the same length with all elements reset. For structs, it assigns a struct with all members reset. In other words, the value of ``a`` after ``delete a`` is the same as if ``a`` would be declared without assignment, with the following caveat:
``delete`` has no effect on whole mappings (as the keys of mappings may be arbitrary and are generally unknown). So if you delete a struct, it will reset all members that are not mappings and also recurse into the members unless they are mappings. However, individual keys and what they map to can be deleted. ``delete`` has no effect on mappings (as the keys of mappings may be arbitrary and are generally unknown). So if you delete a struct, it will reset all members that are not mappings and also recurse into the members unless they are mappings. However, individual keys and what they map to can be deleted: If ``a`` is a mapping, then ``delete a[x]`` will delete the value stored at ``x``.
It is important to note that ``delete a`` really behaves like an assignment to ``a``, i.e. it stores a new object in ``a``. It is important to note that ``delete a`` really behaves like an assignment to ``a``, i.e. it stores a new object in ``a``.
This distinction is visible when ``a`` is reference variable: It will only reset ``a`` itself, not the
value it referred to previously.
:: ::
@ -1067,7 +1069,7 @@ It is important to note that ``delete a`` really behaves like an assignment to `
function f() public { function f() public {
uint x = data; uint x = data;
delete x; // sets x to 0, does not affect data delete x; // sets x to 0, does not affect data
delete data; // sets data to 0, does not affect x which still holds a copy delete data; // sets data to 0, does not affect x
uint[] storage y = dataArray; uint[] storage y = dataArray;
delete dataArray; // this sets dataArray.length to zero, but as uint[] is a complex object, also delete dataArray; // this sets dataArray.length to zero, but as uint[] is a complex object, also
// y is affected which is an alias to the storage object // y is affected which is an alias to the storage object
@ -1096,12 +1098,15 @@ makes sense semantically and no information is lost: ``uint8`` is convertible to
(because ``uint256`` cannot hold e.g. ``-1``). (because ``uint256`` cannot hold e.g. ``-1``).
Any integer type that can be converted to ``uint160`` can also be converted to ``address``. Any integer type that can be converted to ``uint160`` can also be converted to ``address``.
For more details, please consult the sections about the types themselves.
Explicit Conversions Explicit Conversions
-------------------- --------------------
If the compiler does not allow implicit conversion but you know what you are If the compiler does not allow implicit conversion but you know what you are
doing, an explicit type conversion is sometimes possible. Note that this may doing, an explicit type conversion is sometimes possible. Note that this may
give you some unexpected behaviour so be sure to test to ensure that the give you some unexpected behaviour and allows you to bypass some security
features of the compiler, so be sure to test that the
result is what you want! Take the following example where you are converting result is what you want! Take the following example where you are converting
a negative ``int8`` to a ``uint``: a negative ``int8`` to a ``uint``:
@ -1200,3 +1205,5 @@ Addresses
As described in :ref:`address_literals`, hex literals of the correct size that pass the checksum As described in :ref:`address_literals`, hex literals of the correct size that pass the checksum
test are of ``address`` type. No other literals can be implicitly converted to the ``address`` type. test are of ``address`` type. No other literals can be implicitly converted to the ``address`` type.
Explicit conversions from ``bytes20`` or any integer type to ``address`` results in ``address payable``.