c++ g function (INTERNAL)
gfunc_cpp2(dist_mat, start, end, step, width, Lt, n, wc, wr)
A numeric vector with the values of the g function evaluated at the required distances
A square matrix with the distances between points
A float, the start value for evaluating the g-function
A float, the last value for evaluating the g-function
A float, the jump between two evaluations of the k-function
The width of each donut
The total length of the network
The number of points
The weight of the points represented by the columns (destinations)
The weight of the points represented by the rows (origins)