

   PPaarreenntthheesseess aanndd BBrraacceess

        ( ... )

        { ... }

   DDeessccrriippttiioonn::

        Open parenthesis, `(', and open brace, `{', are `.Prim-
        itive' functions in R.

        Effectively, `(' is semantically equivalent to the
        identity `function(x) x', whereas `{' is slightly more
        interesting, see examples.

   SSeeee AAllssoo::

        `if', `return', etc for other objects used in the R
        language itself.

