tt>RooAbsArg</tt> function objects of any type
<pre>
    "RooGaussian::g(x,m,s)"  -- Create a RooGaussian named g with variables x,m,s
                                This expression maps 1-1 to a createArg() call

    "Gaussian::g(x,m,s)"     -- Idem. The 'Roo' prefix on any class may be omitted

    "Gaussian(x,m,s)"        -- Create a RooGaussian with an automatically assigned name with variables x,m,s

</pre>

<li> Expressions with curly brackets creates <tt>RooArgSet</tt>s or <tt>RooArgList</tt>s <tt>"