2直截了当的问题 [英] 2 straight forward Questions
问题描述
正确，
1：是否有包含矩阵和复数的标准库。我需要找到一个3x3矩阵的特征值。
2：有没有办法从<获取指向数组开头的指针br />
存储在std向量中的数据。我在
时刻将一堆浮点数加载到一个向量中来存储openGL的顶点信息，但为了渲染它们，我需要
将一个指针传递给一个开头。数组到OpenGL，而不是向量。在
时刻，我只是将它们变成了另一个阵列，但这似乎有点浪费了：b / b
$ b vector< float>顶点;
//将数据复制到''顶点''
然后在渲染之前我必须：
float * pVertexArray = new float [vertices.size（）];
for（int i = 0; i< vertices.size（）; i ++）pVertexArray [i] = vertices [i];
但这看起来很傻！
谢谢Mike。
" Michael" < SL *********** @ hotmail.com>在消息中写道
news：c7 ********** @ hercules.btinternet.com ...Righty，
1：是否有包含矩阵和复数的标准库。
我需要找到3x3矩阵的特征值。
头文件中有复杂的数字< complex>
std :: complex< double> c（1.0,2.0）;
std :: complex< double> d = c * c;
等
没有这样的矩阵。但是你有很多选择。你可以
写一个简单的类来完成你所需要的一切（我认为这是最好的）。或者
你可以使用矢量向量。你可以使用valarray。
2：有没有办法从
获取指向数组开头的指针存储在std向量中的数据。
是的。
我在
时刻将载荷加载到矢量中以存储openGL的顶点信息，但要渲染它们，我需要
将指向数组开头的指针传递给OpenGL，而不是向量。在
的那一刻，我只是将它们压缩成另一个阵列，但这似乎是浪费的
：
vector< float>顶点;
//将数据复制到''顶点''
然后在渲染之前我必须：
float * pVertexArray = new float [vertices.size（ ）];
for（int i = 0; i< vertices.size（）; i ++）pVertexArray [i] = vertices [i];
但这看起来很傻！
对，就这样做
some_function（& vectices [0]）;
john
Michael写道：Righty，
1：是否有包含矩阵的标准库
不，但是有很多可用的第三方库，其中许多是开源的。试试Google。
和复数。
#include< complex>
我需要找到3x3矩阵的特征值。
2：有没有从存储在std向量中的
数据获取指向数组开头的方法。
" Michael" < SL *********** @ hotmail.com>在消息中写道
news：c7 ********** @ hercules.btinternet.com ...Righty，
1：是否有包含矩阵和复数的标准库。我需要找到3x3矩阵的特征值。
有std :: complex类（#include< complex>）
没有类这样的矩阵，但你可以看看valarray。
2：有没有办法从存储在std向量中的
数据中获取指向数组开头的指针。我在
时刻将大量浮点数加载到向量中以存储openGL的顶点信息，但为了渲染它们，我需要将指向数组开头的指针传递给OpenGL，而不是向量。在
时刻，我只是将它们编成另一个阵列，但这似乎有点浪费：
vector< float>顶点;
//将数据复制到''顶点''
然后在渲染之前我必须：
float * pVertexArray = new float [vertices.size（ ）];
for（int i = 0; i< vertices.size（）; i ++）pVertexArray [i] = vertices [i];
& vec [0]会给你指向第一个元素的指针。
-Sharad
Righty,
1: Is there a standard library that contain matrices and complex numbers. I
need to find eigen values of a 3x3 matrix.
2: Is there a way of getting the pointer to the start of an array from the
data stored in a std vector. I load loads of floats into a vector at the
moment to store vertex infomration for openGL, but to render them, I need to
pass a pointer to the beginning of the array to OpenGL, not a vector. At the
moment I''m just compying them into another array, but this seems like a bit
of a waste:
vector<float> vertices;
//Copy data into ''vertices''
Then before rendering I have to :
float* pVertexArray = new float[vertices.size()];
for(int i=0;i< vertices.size();i++) pVertexArray[i] = vertices[i];
But this seems silly!
Thanks Mike.
"Michael" <sl***********@hotmail.com> wrote in message
news:c7**********@hercules.btinternet.com...Righty,
1: Is there a standard library that contain matrices and complex numbers. I need to find eigen values of a 3x3 matrix.
There are complex numbers in the header file <complex>
std::complex<double> c(1.0, 2.0);
std::complex<double> d = c*c;
etc.
There are no matrices as such. But you have a lot of options. You could
write a simple class that does all you need (I think that would be best). Or
you could use a vector of vectors. Of you could use valarray.
2: Is there a way of getting the pointer to the start of an array from the data stored in a std vector.
Yes.
I load loads of floats into a vector at the
moment to store vertex infomration for openGL, but to render them, I need to pass a pointer to the beginning of the array to OpenGL, not a vector. At the moment I''m just compying them into another array, but this seems like a bit of a waste:
vector<float> vertices;
//Copy data into ''vertices''
Then before rendering I have to :
float* pVertexArray = new float[vertices.size()];
for(int i=0;i< vertices.size();i++) pVertexArray[i] = vertices[i];
But this seems silly!
Right, just do this
some_function(&vectices[0]);
john
Michael wrote:Righty,
1: Is there a standard library that contain matrices
No, but there are plenty of third-party libraries available, many of
them open source. Try Google.
and complex numbers.
#include <complex>
I need to find eigen values of a 3x3 matrix.
2: Is there a way of getting the pointer to the start of an array from the
data stored in a std vector.
&v[0]; // Not sure the standard mandates this, but I think there''s a DR.
"Michael" <sl***********@hotmail.com> wrote in message
news:c7**********@hercules.btinternet.com...Righty,
1: Is there a standard library that contain matrices and complex numbers. I
need to find eigen values of a 3x3 matrix.
There is std::complex class (#include <complex>)
No class as such for matrices but you could take a look at valarray.
2: Is there a way of getting the pointer to the start of an array from the
data stored in a std vector. I load loads of floats into a vector at the
moment to store vertex infomration for openGL, but to render them, I need to
pass a pointer to the beginning of the array to OpenGL, not a vector. At the
moment I''m just compying them into another array, but this seems like a bit
of a waste:
vector<float> vertices;
//Copy data into ''vertices''
Then before rendering I have to :
float* pVertexArray = new float[vertices.size()];
for(int i=0;i< vertices.size();i++) pVertexArray[i] = vertices[i];
&vec[0] will give you the pointer to the first element.
-Sharad
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