C++ 使用数组向量的正确方法
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Correct way to work with vector of arrays
提问by Pulkit Sinha
Could someone tell what is the correct way to work with a vector of arrays?
有人能说出使用数组向量的正确方法是什么吗？
I declared a vector of arrays (vector<float[4]>) but got error: conversion from 'int' to non-scalar type 'float [4]' requestedwhen trying to resizeit. What is going wrong?
我声明了一个数组向量 ( vector<float[4]>) 但error: conversion from 'int' to non-scalar type 'float [4]' requested在尝试时得到resize了。出了什么问题？
回答by James McNellis
You cannot store arrays in a vectoror any other container. The type of the elements to be stored in a container (called the container's value type) must be both copy constructible and assignable. Arrays are neither.
您不能将数组存储在vector或任何其他容器中。要存储在容器中的元素的类型（称为容器的值类型）必须是可复制构造和可赋值的。数组两者都不是。
You can, however, use an arrayclass template, like the one provided by Boost, TR1, and C++0x:
但是，您可以使用array类模板，例如 Boost、TR1 和 C++0x 提供的类模板：
std::vector<std::array<double, 4> >
(You'll want to replace std::arraywith std::tr1::arrayto use the template included in C++ TR1, or boost::arrayto use the template from the Boost libraries. Alternatively, you can write your own; it's quite straightforward.)
（您想更换std::array与std::tr1::array使用包含在C ++ TR1的模板，或者boost::array使用从Boost库的模板或者，你可以写你自己的。这是非常简单的。）
回答by Nawaz
Use:
用：
vector<vector<float>> vecArray; //both dimensions are open!
回答by Nawaz
There is no error in the following piece of code:
下面这段代码没有错误：
float arr[4];
arr[0] = 6.28;
arr[1] = 2.50;
arr[2] = 9.73;
arr[3] = 4.364;
std::vector<float*> vec = std::vector<float*>();
vec.push_back(arr);
float* ptr = vec.front();
for (int i = 0; i < 3; i++)
printf("%g\n", ptr[i]);
OUTPUT IS:
输出是：
6.28
6.28
2.5
2.5
9.73
9.73
4.364
4.364
IN CONCLUSION:
综上所述：
std::vector<double*>
is another possibility apart from
是另一种可能
std::vector<std::array<double, 4>>
that James McNellis suggested.
詹姆斯麦克内利斯建议。
回答by Mark Ransom
Every element of your vector is a float[4], so when you resize every element needs to default initialized from a float[4]. I take it you tried to initialize with an intvalue like 0?
向量的每个元素都是 a float[4]，因此当您调整大小时，每个元素都需要从 a 进行默认初始化float[4]。我认为您尝试使用int类似的值进行初始化0？
Try:
尝试：
static float zeros[4] = {0.0, 0.0, 0.0, 0.0};
myvector.resize(newsize, zeros);
