从float *转换为vector< float> [英] convert from float* to vector<float >

问题描述

我有一个功能 float * pointwise_search(vector<float > &P,vector<float > &Q,float* n, int len ).

我想用matlab调用它，所以我需要编写一个mexFunction.

I want matlab call it so I need to write a mexFunction.

void mexFunction(int nlhs, mxArray *plhs[], int nrhs, const mxArray *prhs[]) 
{ 
    if (nrhs != 4)
    {
        mexErrMsgTxt("Input is wrong!");
    }

    float *n = (float*) mxGetData(prhs[2]);
    int len = (int) mxGetScalar(prhs[3]);
    vector<float > Numbers= (vector<float >)mxGetPr(prhs[0]);
    vector<float > Q= (vector<float >)mxGetPr(prhs[1]);

    plhs[1] = pointwise_search(Numbers,Q,n,len );

  }

但是我发现vector<float > Numbers= (vector<float >)mxGetPr(prhs[0]); vector<float > Q= (vector<float >)mxGetPr(prhs[1]);是错误的.

But I found that vector<float > Numbers= (vector<float >)mxGetPr(prhs[0]); vector<float > Q= (vector<float >)mxGetPr(prhs[1]); are wrong.

所以我必须将float * pointwise_search(vector<float > &P,vector<float > &Q,float* n, int len )更改为float * pointwise_search(float *P,float *Q,float* n, int len ).

根据答案，我将其重写为以下内容

According to the answers, I rewrite as the following

 float * pointwise_search(float p,float *q,int num_thres, float n, int len ) 
{    vector<float> P{p, p + num_thres}; 
     vector<float> Q{q, q + num_thres}; 
     int size_of_threshold = P.size();
...
} 

但是会发生错误.

pointwise_search.cpp(12) : error C2601: 'P' : local function definitions are illegal pointwise_search.cpp(11): this line contains a '{' which has not yet been matched

pointwise_search.cpp(12) : error C2601: 'P' : local function definitions are illegal pointwise_search.cpp(11): this line contains a '{' which has not yet been matched

作为评论，我应该将vector<float> P{p, p + num_thres};更改为vector<float> P(p, p + num_thres);. :)

As the comment,I should change vector<float> P{p, p + num_thres}; to vector<float> P(p, p + num_thres);. :）

推荐答案

当然，您通常不能将指针转换为vector，它们是不同的东西.但是，如果指针包含已知长度的C样式数组的第一个元素的地址，则可以创建一个vector，其内容与该数组相同，如下所示:

Of course you can not generally convert a pointer to a vector, they are different things. If however the pointer holds the address of the first element of a C-style array of known length, you can create a vector with the same contents as the array like:

std::vector<float> my_vector {arr, arr + arr_length};

其中，arr是指针，而arr_length是数组的长度.然后，您可以将vector传递给期望std::vector<float>&的函数.

where arr is said pointer and arr_length is the length of the array. You can then pass the vector to the function expecting std::vector<float>&.

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