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Merge pull request #8026 from ethereum/updateOperators06

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Update operators for 0.6.0.
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Alex Beregszaszi 2019-12-16 17:12:44 +00:00 committed by GitHub
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docs/types/operators.rst
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@ -3,9 +3,14 @@
Operators Involving LValues
===========================
If ``a`` is an LValue (i.e. a variable or something that can be assigned to), the following operators are available as shorthands:
If ``a`` is an LValue (i.e. a variable or something that can be assigned to), the
following operators are available as shorthands:
``a += e`` is equivalent to ``a = a + e``. The operators ``-=``, ``*=``, ``/=``, ``%=``, ``|=``, ``&=`` and ``^=`` are defined accordingly. ``a++`` and ``a--`` are equivalent to ``a += 1`` / ``a -= 1`` but the expression itself still has the previous value of ``a``. In contrast, ``--a`` and ``++a`` have the same effect on ``a`` but return the value after the change.
``a += e`` is equivalent to ``a = a + e``. The operators ``-=``, ``*=``, ``/=``, ``%=``,
``|=``, ``&=`` and ``^=`` are defined accordingly. ``a++`` and ``a--`` are equivalent
to ``a += 1`` / ``a -= 1`` but the expression itself still has the previous value
of ``a``. In contrast, ``--a`` and ``++a`` have the same effect on ``a`` but
return the value after the change.
.. _delete:
@ -19,12 +24,20 @@ initial value. ``delete a[x]`` deletes the item at index ``x`` of the array and
all other elements and the length of the array untouched. This especially means that it leaves
a gap in the array. If you plan to remove items, a :ref:`mapping <mapping-types>` is probably a better choice.
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:
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 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``.
``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
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.
::