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author | chriseth <chris@ethereum.org> | 2018-09-20 20:00:01 +0800 |
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committer | chriseth <chris@ethereum.org> | 2018-09-20 20:00:01 +0800 |
commit | cb7866916ec54d3a4969f9b6ef9af74779f74a46 (patch) | |
tree | 62e7667b25f69d65848f5b6c23260683472852df | |
parent | 2150aea344c259eb6541cb3617e7ae0f3d3381dd (diff) | |
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[DOCS] Final updates to types section.
-rw-r--r-- | docs/types.rst | 15 |
1 files changed, 11 insertions, 4 deletions
diff --git a/docs/types.rst b/docs/types.rst index 1cbbb1be..b6ee6593 100644 --- a/docs/types.rst +++ b/docs/types.rst @@ -1050,11 +1050,13 @@ If ``a`` is an LValue (i.e. a variable or something that can be assigned to), th 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``. +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 { uint x = 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; 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 @@ -1096,12 +1098,15 @@ makes sense semantically and no information is lost: ``uint8`` is convertible to (because ``uint256`` cannot hold e.g. ``-1``). 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 -------------------- 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 -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 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 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``.
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