Function to make queries using pre-computed trees

[elipickh]

It would be useful to have a dedicated function in C++/R to make queries on trees that have already been computed. This would especially help when making many repeated queries and when we would prefer separate objects/processes for trees and queries.

For example:

library(RANN2)
p1=kcpoints[[1]]
w1=WANN(p1)
q = t(c(1.0, 1.0, 1.0))

We can query by doing, e.g., w1$query(q, 1, 0.0), which works well (and is very fast).

However, instead of using the above R5 class function, I would like to have a simpler function that can input the tree directly, as a separate object. So something like:

// [[Rcpp::export]]
List wann_query(?? kd_tree_object, NumericMatrix query, const int k) {

//Skip the tree-building process and proceed to calculate distances, as in nn.cpp
//WANN tree = WANN(data);  -- This line would not be needed

return List::create(Rcpp::Named("nn.idx")=ridx, Rcpp::Named("nn.dists")=rdists);
}

The main challenges I'm facing are

1. How to extract the tree from the w1 WANN object?
2. How exactly can the tree object be passed into wann_query and used to calculate distances?

The end goal would be something like:

tree_out <- w1$tree
wann_query(tree_out, q, 1)
# Output identical to 
w1$query(q, 1, 0.0)

[caiohamamura]

Why not pass w1 to wann_query and inside it just return the result of w1$query(q, 1, 0.0)?