Andy Little wrote:
I've had a quick look. It looks like a very classical matrix library. There are some issues
#include <entropy/linear_algebra.hpp>
using entropy::vector; int main() { vector<double,2> v1(1.,2.,3.); }
This causes the program to crash when run, so I presume some compile time asserts would be mandatorry.
I am aware of this problem. If submitted to boost I would probably use the boost preprocessor and mpl's enable_if to make only the constructor whose number of arguments matched be available in the class. The reason that such measures are not in place now is that I wanted to keep library dependencies low and the code tidy.
Overall though it looks very clean. In fact its almost the exact opposite of my own geometry library in the vault.
This brings me to a problem I have been wrestling with:
As author of pqs physical quantities library I am pretty much required to implement a geometry library so that it can use physical quantities as value_types, but I dont feel it reasonable that I should impose that on everybody.
The fact that my library allows use of physical quantities as value_types has repurcussions in terms of the interface (no operator[]) and the implementation (Look at the comparative zip file sizes).
What exactly does using physical quantities entail? Is the problem that performing matrix multiplication results in the types of the physical quantities becoming mangled, and if so couldn't you just make matrices use untyped units while allowing the vectors to keep their types? For instance (note that I am using row vectors and assuming the meta function remove_units has been implemented): template < typename VecType, std::size_t Size > vector < VecType, Size > & operator *= ( const vector < VecType, Size > & v, const matrix < remove_units < VecType >::type, Size, Size > & mat ) { vector < VecType, Size > prev ( *this ); for ( std::size_t c = 0; c < Size; ++c ) { this->data[c] = 0; for ( std::size_t r = 0; r < Size; ++r ) { // type times a scalar results in the same type // type + type results in the same type this->data[c] += prev->data[r] * mat[r][c]; } } return *this; } -Jason