Question

i’m using Armadillo lib for linear algebra and i’m new to c++.

need to serialize some matrix in std::String (for save it in some xml) and there some ready method that take a stream.

due to the fact that i’m not used to read c++ code full of streamstring operation (i am a python programmer) i decided to make some methods that work with string and hide the stream stuffs for improve my code readability.

for make an improvment in my c++ knowledge i decide to try the use of template for make one method for all armadillo classes: mat, rowvec, colvec (they all have .load() and .save())

i decided to write those methods in a separate file utils.h, it should be usefull in future project too!

the problem is with the second method:

using namespace std;

// 1°
template<typename Matrix>
string matrix_to_string(Matrix& m) {
    stringstream ss;
    m.save(ss, arma::arma_ascii);
    return ss.str();
}

// 2°
template<typename Matrix>
Matrix matrix_from_string(string& s) {
    stringstream ss;
    ss << s;
    Matrix m;
    m.load(ss, arma::arma_ascii);
    return m;
}

the first method works perfectly, but with the second one.. if i try to use it i get the error:

no matching function for call to ‘matrix_from_string(std::string&)’

i’m calling it in this way:

mat prior;
string s = XML.getValue("prior", ""); // my XML lib, it works fine
prior = matrix_from_string( s );

what’s happening?

Answer 1

Change the line

prior = matrix_from_string( s );

to

prior = matrix_from_string<mat>(s);