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Remove length related FAQ item

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Chris Ward 2018-11-15 12:11:25 +01:00
parent 9db76403bb
commit 9b657134ef
2 changed files with 3 additions and 45 deletions
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44
docs/frequently-asked-questions.rst
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@ -325,50 +325,6 @@ to create an independent copy of the storage value in memory.
On the other hand, ``h(x)`` successfully modifies ``x`` because only
a reference and not a copy is passed.
Sometimes, when I try to change the length of an array with ex: ``arrayname.length = 7;`` I get a compiler error ``Value must be an lvalue``. Why?
==================================================================================================================================================
You can resize a dynamic array in storage (i.e. an array declared at the
contract level) with ``arrayname.length = <some new length>;``. If you get the
"lvalue" error, you are probably doing one of two things wrong.
1. You might be trying to resize an array in "memory", or
2. You might be trying to resize a non-dynamic array.
::
pragma solidity >=0.4.18 <0.6.0;
// This will not compile
contract C {
int8[] dynamicStorageArray;
int8[5] fixedStorageArray;
function f() public {
int8[] memory memArr; // Case 1
memArr.length++; // illegal
int8[5] storage storageArr = fixedStorageArray; // Case 2
storageArr.length++; // illegal
int8[] storage storageArr2 = dynamicStorageArray;
storageArr2.length++; // legal
}
}
**Important note:** In Solidity, array dimensions are declared backwards from the way you
might be used to declaring them in C or Java, but they are access as in
C or Java.
For example, ``int8[][5] somearray;`` are 5 dynamic ``int8`` arrays.
The reason for this is that ``T[5]`` is always an array of 5 ``T``'s,
no matter whether ``T`` itself is an array or not (this is not the
case in C or Java).
Is it possible to return an array of strings (``string[]``) from a Solidity function?
=====================================================================================

4
docs/types.rst
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@ -913,7 +913,9 @@ Members
For dynamically-sized arrays (only available for storage), this member can be assigned to resize the array.
Accessing elements outside the current length does not automatically resize the array and instead causes a failing assertion.
Increasing the length adds new zero-initialised elements to the array.
Reducing the length performs an implicit :ref:``delete`` on each of the removed elements.
Reducing the length performs an implicit :ref:``delete`` on each of the
removed elements. If you try to resize a non-dynamic array that isn't in
storage, you receive a ``Value must be an lvalue`` error.
**push**:
Dynamic storage arrays and ``bytes`` (not ``string``) have a member function called ``push`` that you can use to append an element at the end of the array. The element will be zero-initialised. The function returns the new length.
**pop**: