---
title: "Knowledge base"
date: "`r Sys.Date()`"
output: rmarkdown::html_vignette
vignette: >
  %\VignetteIndexEntry{Knowledge base}
  %\VignetteEngine{knitr::rmarkdown}
  %\VignetteEncoding{UTF-8}
---

```{r setup, include = FALSE}
knitr::opts_chunk$set(
  collapse = TRUE,
  comment = "#>"
)
```

This article is a knowledge base for the`{rSharp}` package. It is a collection of 
useful information that may help troubleshooting and understanding the package.

## Loading the workspace

Saving the RStudio workspace (which is the default option on RStudio exit) will save 
the R6 objects, but the pointers to .NET objects will be lost. Trying to access the 
objects after loading a workspace will result in an error. There is currently no
workaround for saving .NET objects.

## Data type conversion

- `NA` is a concept of marking "missing values" in R which is not available in .NET.
What might appear conterintuitive is that `NA` has a type "logical" and is interpreted as 
`TRUE` when sent to .NET. Attention should be payed when sending `NA` to .NET methods.
- If the signature of a .NET method require an integer argument, it must be passed as an integer using `as.integer()` from R. R assumes all numerics as doubles by default, and will cause an error if passed to a method that expects an integer.
- Objects in R are vectors, and single values are just a particular case of vectors 
of length one. In the .NET, scalar values and arrays are different types.  In current implementation, 
an R vector with length >1 will be translated to an array in the .NET, a length 
of one becomes a scalar value. This might lead to problems when calling .NET methods
expecting a an array when passing a vector of 1.
- When trying to pass a vector containing a `NULL` from R to .NET, the `NULL` will be
removed from the vector. This is how R treats `NULL` in vectors. E.g., trying 
to call a .NET method with an argument that expects an array of doubles with a vector
`c(0, NULL, 3)` will result in a call with `c(0, 3)`. In order to correctly pass 
`NULL` to .NET, it should be passed as a list: `list(0, NULL, 3)`.