If `poly-markdown.el` is loaded. This should work by default. Otherwise `M-x
poly-markdown+r-mode RET` should do the job.

```r
1 + 1
```

```r
## [1] 2

```

```r
 0.4 - 0.7 + 0.3  # what? it is not zero!
```

```r
## [1] 5.551e-17
```

```emacs-lisp
(message  "it works")
```

```javascript
{
    
}
```

  ```python
    if len($declaration) > 0 and $declaration::isTypedef:
        $Symbols::types.add($IDENTIFIER.text)
        print "define type "+$IDENTIFIER.text  # line 19
  ```