limitations of the 'let' operation?

[healyp]

Hello pgf users,

According to the manual I can use the 'let' operation to create numbers and points.  What I would like to do is to create nodes temporarily (circles, actually) within a \foreach macro.  Is something like this possible?

More specifically, I would like to be able to achieve something like the following snippet of code (which fails compilation) for marking the intersections of two sets of concentric circles (level curves).

\foreach \rad in {.1cm,.2cm,.3cm,.4cm,.5cm}
{
  \path let \n1 = {0.5cm+\rad}, \p1 = (-30:\n1) in
  node (m1) at (c1) [circle through=(\p1)] {};  % not allowed, it seems
  \path let \n2 = {1.5cm+\rad}, \p2 = (230:\n2) in
  node (m2) at (c2) [circle through=(\p2)] {};  % ditto

  \coordinate [label=-135:$y$] (y) at (intersection 2 of m1 and m2);
  \fill [red] (y) circle (1pt);
}

If somebody could advise me on how I can compute these circle intersections within the \foreach macro I'd be most grateful.

Thanks to all,
Patrick Healy

[Till Tantau-3]

Hi!

works for me. The following compiles fine and gives the expected  
(correct) results:


\documentclass[10pt,oneside]{article}

\usepackage{tikz}
\usetikzlibrary{calc,through}
\begin{document}

\begin{tikzpicture}

   \coordinate (c1) at (0,0);
   \coordinate (c2) at (-1,0);

   \foreach \rad in {.1cm,.2cm,.3cm,.4cm,.5cm}
   {
     \path let \n1 = {0.5cm+\rad}, \p1 = (-30:\n1) in
     node (m1) at (c1) [circle through=(\p1)] {};  %
     \path let \n2 = {1.5cm+\rad}, \p2 = (230:\n2) in
     node (m2) at (c2) [circle through=(\p2)] {};  %

     \coordinate [label=-135:$y$] (y) at (intersection 2 of m1 and m2);
     \fill [red] (y) circle (1pt);
   }
\end{tikzpicture}

\end{document}


Regards,
Till

Am 17.07.2008 um 11:49 schrieb healyp:

>
> Hello pgf users,
>
> According to the manual I can use the 'let' operation to create  
> numbers and
> points.  What I would like to do is to create nodes temporarily  
> (circles,
> actually) within a \foreach macro.  Is something like this possible?
>
> More specifically, I would like to be able to achieve something like  
> the
> following snippet of code (which fails compilation) for marking the
> intersections of two sets of concentric circles (level curves).
>
> \foreach \rad in {.1cm,.2cm,.3cm,.4cm,.5cm}
> {
>  \path let \n1 = {0.5cm+\rad}, \p1 = (-30:\n1) in
>  node (m1) at (c1) [circle through=(\p1)] {};  % not allowed, it seems
>  \path let \n2 = {1.5cm+\rad}, \p2 = (230:\n2) in
>  node (m2) at (c2) [circle through=(\p2)] {};  % ditto
>
>  \coordinate [label=-135:$y$] (y) at (intersection 2 of m1 and m2);
>  \fill [red] (y) circle (1pt);
> }
>
> If somebody could advise me on how I can compute these circle  
> intersections
> within the \foreach macro I'd be most grateful.
>
> Thanks to all,
> Patrick Healy
>
> --
> View this message in context: http://www.nabble.com/limitations-of-the-%27let%27-operation--tp18505015p18505015.html
> Sent from the pgf-users mailing list archive at Nabble.com.
>
>
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--
Prof. Dr. Till Tantau <tantau@...>
http://www.tcs.uni-luebeck.de


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