[feature request] optional passing by reference

[dselivanov]

In general it is not desirable to change arguments in-place, but in some cases it is useful (when you now what you do). So mb it is possible to add by_reference = FALSE argument to type annotations to control how arguments are passed? and if by_reference then function signature might be F(arma::mat &x) instead of F(arma::mat x)

[dirkschumacher]

Sounds like a good idea to use the type hints to control that. Currently a const ref is used by default unless the code mutates the parameter, then it is changed to a copy.

library(armacmp)
translate(function(X, Y) {
  X <- X + 1
  return(X + Y)
}, "test")
#> R function
#> 
#> function (X, Y) 
#> {
#>     X <- X + 1
#>     return(X + Y)
#> }
#> 
#> C++ function translation
#> 
#> arma::mat test(arma::mat X, const arma::mat& Y)
#> {
#> X = X + 1.0;
#> return X + Y;
#> }
#> 

^{Created on 2019-12-26 by the reprex package (v0.3.0)}