Defining functions for TikZ

The "easiest" way I've found to define "functions" in TikZ is to use the LaTeX \newcommand outside of the \tikzpicture environment.

\newcommand{\cir}[3]{ \def \x{ (#1,#2) circle (#3cm) } \draw \x ; }

And then use this inside the tikzpicture as:

\cir{0}{0}{1}

However, since the circle is drawn within the \newcommand, I can't rotate the figure inside the \tikzpicture environment.