How to use parameter numbers and \foreach

Question

Is there a way to use the TikZ \foreach command to do operations with parameters?

E.g. I would like to be able to write (just a silly example):

\newcommand{\foo}[9]{

    \foreach \x in{1,2,...,9}{
        \draw(0,#\x)--++(1,1);

    }
}

where #\x would mean the x th parameter of the command I'm defining with \newcommand.

This should come in handy since I'm writing macros that depend on global values that can be set arbitrarily. E.g. \def\N{9} would go in preamble and I'd write newcommand{\bar}[\N]{...}, but since I don't know beforehand how much parameters there will be, I can't define anything unless I write \foreach \x in{1,2,...,\N} and the above draw command.

---

What I actually like to do:

I'd like to have a command that plots some coordinates which are given. So I'd like \foo{#1}{#2}{#3} to expand to something like;

\draw plot coordinates {(360/\N*1:#1) (360/\N*2:#2) (360/\N*3:#3) ... (360/\N*\N:#N};

but I don't know if this is possible.

Answer 1

I do not reall understand what exactly do you want to draw, but maybe this helps:

\documentclass{minimal}
\usepackage{tikz}

\makeatletter
\def\foo#1{\foo@i#1,,\@nil}%
\def\foo@i#1,#2,#3\@nil{%
  \draw(0,#1)--++(1,1);
  \ifx\relax#2\relax\else\foo@i#2,#3\@nil\fi}
\makeatother

\begin{document}
\begin{tikzpicture}
\foo{1,2,3,4,5,6,7,8,9}
\end{tikzpicture}
\begin{tikzpicture}
\foo{1,2,3,4,5,6}
\end{tikzpicture}

\end{document}

Answer 2

(Substantially revised answer.) The following should read in and draw as many arguments as you like, one at a time, provided that \N is defined and stores a positive integer.

\makeatletter
  \newcount\c@foo
  \newcommand\foo{%
    \c@foo=1\relax
    \@foo}
  \newcommand\@foo[1]{%
    \draw(0,#1)--++(1,1);%
    \advance\c@foo by 1\relax%
    \ifnum\c@foo>\N%
       \let\@tempa\relax
    \else
       \let\@tempa\@foo
    \fi
    \@tempa}
\makeatother