# Is the R interface identical to R in a R.<x> assignment?

`R`

is a builtin identifier in Sage and refers to the `r`

interface :

```
sage: R
sage.interfaces.r.R
sage: r
R Interpreter
```

Now I was wondering if the later R is related to the R letter used in a left hand side assignment for instance :

```
R.<x> = ZZ[]
```