Problems with unlocking binding (in R) after running code from c++ - c++

Question

So I put some code into c++ from R in order to make my model run faster. The c++ code returns a list of 2 items: one vector called "trace" and one matrix called "weights". Once the c++ code has run I would like to reassign "weights" and "trace" in R to the values that were computed from the c++ code. Unfortunately, when I tried to do this I got the error: "Error: cannot change value of locked binding for 'weights'". So I searched for an unbinding function and found unlockBinding. I stuck that in my R code, but I am still getting the same error as before! Am I putting the unlockBinding function in the wrong place? Am I using it correctly? The items "weights" and "trace" do exist in the global environment so why are they not unlocking?
I assigned the list that the c++ code returns to the variable "result", then I used the unlockBinding function, then I reassigned "weights" and "trace" to be what was computed in the c++ code. Here is the code:
batch <- function(n.training){
for(i in 1:n.training){
g <- input.correlation()
for(o in 1:nrow(g)){
result <- traceUpdate(g[o,], trace, weights, trace.param, learning.rate)
unlockBinding("weights", .GlobalEnv)
unlockBinding("trace", .GlobalEnv)
weights <<- result$weights
trace <<- result$trace
}
}
}
Here is the part of my C++ code that returns a list of 2 items, one being a matrix "weights" and the other being a vector "trace":
List traceUpdate(NumericVector input, NumericVector trace, NumericMatrix weights, double traceParam, double learningRate){
NumericVector output = forwardPass(input, trace.size(), weights);
for(int i = 0; i<trace.size(); i++){
trace[i] = (1 - traceParam) * trace[i] + traceParam * output[i];
for(int j=0; j<input.size(); j++){
double w = weights(j,i);
if(w >= 0){
weights(j,i) = w + learningRate * trace[i] * input[j] - learningRate * trace[i] * w;
}
}
}
//return weights
return List::create(Rcpp::Named("weights") = weights,
Rcpp::Named("trace") = trace);
}
If I simply reassign the weights like this:
weights <- matrix(0, nrow = 100, ncol = 20)
they do all change to zeroes and I do not get an error.
Also, when looking for solutions online I came across a way to unlock environments in R, but I'm pretty sure that's not what's wrong because the environment is not locked.
I'm new to this site and relatively new to programming so I apologize if my question is dumb or formatted incorrectly etc.
Thank you.

Answer 1

Just received a solution from my professor:
"Instead of treating weights and trace as global variables that are modified from inside the batch function, we can pass them into the function and return them out:"
batch <- function(weights, trace, n.training){
for(i in 1:n.training){
g <- input.correlation()
for(o in 1:nrow(g)){
result <- traceUpdate(g[o,], trace, weights, trace.param, learning.rate)
weights <- result$weights
trace <- result$trace
}
}
return(list(weights=weights, trace=trace))
}
result <- batch(weights, trace, 50)
weights <- result$weights
trace <- result$trace