igl::cat

在dim维上，对A和B进行连接。如果dim为1，则将A,B按垂直方向堆叠，如果dim为2,则将A,B按水平方向堆叠。

template <typename Derived, class MatC>
IGL_INLINE void igl::cat(
const int dim,
const Eigen::MatrixBase<Derived> & A,
const Eigen::MatrixBase<Derived> & B,
MatC & C)
{
assert(dim == 1 || dim == 2);
// Special case if B or A is empty
if(A.size() == 0)
{
C = B;
return;
}
if(B.size() == 0)
{
C = A;
return;
}

if(dim == 1)
{
assert(A.cols() == B.cols());
C.resize(A.rows()+B.rows(),A.cols());
C << A,B;
}else if(dim == 2)
{
assert(A.rows() == B.rows());
C.resize(A.rows(),A.cols()+B.cols());
C << A,B;
}else
{
fprintf(stderr,"cat.h: Error: Unsupported dimension %d\n",dim);
}
}

igl::cat(dim,A,B,C);