[英]List initializer
I am trying to declare an iterator of type std::initializer_list
as it is described in this answer . 我试图声明一个类型为std::initializer_list
的迭代器,如本答案所述 。
But I always get this error: 但是我总是会收到这个错误:
error: 'iterator' is not a member of 'std::initializer_list<int>'
How do I declare an iterator of type std::initializer_list
? 如何声明类型为std::initializer_list
的迭代器?
The following code for example will not work. 例如,以下代码将不起作用。 In addition, the compiler that I use supports the new standard draft. 另外,我使用的编译器支持新的标准草案。
int findCommon(std::initializer_list<int> nums)
{
std::initializer_list<int>::iterator it;
for (it = nums.begin() ; it != nums.end() ; ++it)
{
std::cout << *it << std::endl;
}
return 1;
}
You need to add 您需要添加
#include <initializer_list>
and for this example probably also 在这个例子中
#include <iostream>
Also make sure you are using the -std=c++0x
switch to g++. 还要确保您正在使用-std=c++0x
切换到g ++。 And you need at least g++ version 4.4. 而且您至少需要g ++ 4.4版。
When using the compiler from MacPorts, the compiler is called
g++-mp-4.5
or
g++-mp-4.4
.
从MacPorts使用编译器时,编译器称为
(Incorrect assumption). (错误的假设)。 g++-mp-4.5
或
g++-mp-4.4
。
I noticed some recently fixed bugs related to initializer_list
on the GCC bugzilla , so I recommend getting the newest version of GCC, 4.5.1. 我在GCC bugzilla上注意到了一些与initializer_list
相关的最近已修复的错误,因此,我建议获取最新版本的GCC 4.5.1。 Because when using this version I am able to compile both your examples without problems. 因为使用此版本时,我可以毫无问题地编译两个示例。
Your compiler's implementation probably just doesn't have these typedefs (eg with GCC 4.4.1, initializer_list
doesn't contain any typedefs, you can check the header yourself). 您的编译器的实现可能只是没有这些typedef(例如,在GCC 4.4.1中, initializer_list
不包含任何typedef,您可以自己检查标头)。
As a "workaround", use auto
: 作为一种“解决方法”,请使用auto
:
int findCommon(std::initializer_list<int> nums)
{
for (auto it = nums.begin() ; it != nums.end() ; ++it)
{
std::cout << *it << std::endl;
}
return 1;
}
Or rely on initializer_list<T>::iterator
being a synonym for const T*
. 或依靠initializer_list<T>::iterator
作为const T*
的同义词。
You can avoid directly specifying the iterator type, which should lead to cleaner code: 您可以避免直接指定迭代器类型,这会导致代码更简洁:
void f(std::initializer_list<int> nums)
{
for (auto x : nums) {
std::cout << x << '\n';
}
// or:
std::copy(begin(nums), end(nums), std::ostream_iterator(std::cout, "\n"));
}
Range-based for loops are supported in GCC 4.6 . GCC 4.6支持基于范围的for循环。 (Any problem calling them foreach loops, informally?) (是否有非正式地将它们称为foreach循环的问题?)
Including <iterator> may be required for std::begin and std::end, though several headers guarantee they are declared (24.6.5, N3092). std :: begin和std :: end可能需要包含<iterator>,尽管可以保证声明了多个标头(24.6.5,N3092)。
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