[英]Rcpp: ambiguous overload for 'operator=' Matrix and List
The following Rcpp code is the minimal reproducible example for a much larger code that generates the identical compilation error. 以下Rcpp代码是生成相同编译错误的更大代码的最小可重现示例。 It seems that I cannot asign a numeric matrix to a list and the list then again to another matrix.
似乎我无法将数字矩阵设置为列表,然后将列表再次设置为另一个矩阵。
#include <Rcpp.h>
using namespace Rcpp;
//[[Rcpp::export]]
List return_a(NumericMatrix a, NumericMatrix b){
//the function only returns the input matrix a
List result(1);
result(0) = a;
return(result);
}
//[[Rcpp::export]]
List wrapper_cpp(NumericMatrix a, NumericMatrix b){
//the function is a dummy wrapper for much more code
List Step1(1);
List results(1);
Step1 = return_a(a,b);
a = Step1(0);
results(0) = a;
return(results);
}
The code above gives the following compilation error that I shortened: 上面的代码给出了我缩短的以下编译错误:
error: ambiguous overload for 'operator=' (operand types are 'Rcpp::NumericMatrix {aka Rcpp::Matrix<14>}' and 'Rcpp::Vector<19>::Proxy ...
a = Step1(0);
My real function is much more complex. 我的真正功能要复杂得多。 I need to manipulate matrices in several loops and in each step the matrices are returned by each function within a list.
我需要在几个循环中操作矩阵,并且在每个步骤中,矩阵由列表中的每个函数返回。 I then need to extract these lists to manipulate the matrices further.
然后,我需要提取这些列表以进一步操作矩阵。 How can this be done?
如何才能做到这一点?
Besides the error that @Ralf already mentioned, you were simply trying too much. 除了@Ralf已经提到的错误之外,你只是在尝试太多。 Sometimes we need an intermediate step as the template magic is ... finicky.
有时我们需要一个中间步骤,因为模板魔术是......挑剔。 The following works.
以下作品。
#include <Rcpp.h>
using namespace Rcpp;
//[[Rcpp::export]]
List return_a(NumericMatrix a, NumericMatrix b){
//the function only returns the input matrix a
List result(1);
result(0) = a;
return(result);
}
//[[Rcpp::export]]
List wrapper_cpp(NumericMatrix a, NumericMatrix b){
//the function is a dummy wrapper for much more code
List results(1);
List Step1 = return_a(a,b);
NumericMatrix tmp = Step1(0);
results(0) = tmp;
return(results);
}
R> Rcpp::sourceCpp("~/git/stackoverflow/54771818/answer.cpp")
R> wrapper_cpp(matrix(1:4,2,2), matrix(4:1,2,2))
[[1]]
[,1] [,2]
[1,] 1 3
[2,] 2 4
R>
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