Usando \foreach dentro de un comando de dibujo usando TIKZ

Question

Soy nuevo en el uso \foreachpero no en la codificación en general. Siguiendo el código de la respuesta número 40 de este ejemplo:Cómo dibujar una línea tangente de un punto arbitrario en un camino en TikZ

¿Cómo puedo condensar adecuadamente la tangent=0.xlista en la declaración de sorteo?

Probé algunas ideas sin éxito:

\documentclass{standalone}
\usepackage{tikz}
\usetikzlibrary{decorations.markings}
\begin{document}

\begin{tikzpicture}[
tangent/.style={
    decoration={
        markings,% switch on markings
        mark=
            at position #1
            with
            {
                \coordinate (tangent point-\pgfkeysvalueof{/pgf/decoration/mark info/sequence number}) at (0pt,0pt);
                \coordinate (tangent unit vector-\pgfkeysvalueof{/pgf/decoration/mark info/sequence number}) at (1,0pt);
                \coordinate (tangent orthogonal unit vector-\pgfkeysvalueof{/pgf/decoration/mark info/sequence number}) at (0pt,1);
            }
    },
    postaction=decorate
},
use tangent/.style={
    shift=(tangent point-#1),
    x=(tangent unit vector-#1),
    y=(tangent orthogonal unit vector-#1)
},
use tangent/.default=1
]
\draw [
tangent=0.1,
tangent=0.2,
tangent=0.3,
tangent=0.4,
tangent=0.5,
tangent=0.6,
tangent=0.7,
tangent=0.8,
tangent=0.9,
%%%% attempt 1
%tangent={0.05,0.01,...0.95}
%%%%% attempt 2
%\foreach \y in {0.1,0.2,...,0.9}
%{
%tangent=\y,
%}
] (0,0) arc (180:0:10);

\foreach \x [count=\xi] in {1,1,2,1,2,1,4,3,1.5}
{
\draw [red, thick,->, use tangent=\xi] (0,0) -- (0,-1*\x);
}
\end{tikzpicture}
\end{document}

para obtener un resultado como este:

¿Cómo puedo condensar correctamente la lista tangente=0.x, en la declaración de dibujo?

Answer 1

Cuando necesite llamar a la misma tecla repetidamente, puede usar <key>/.list={<foreach expression>}, donde <foreach expression>puede ser una lista simple o una lista con puntos suspensivos. Entonces, en este caso, puedes usar\draw [tangent/.list={0.1,0.2,...,0.9}](0,0) arc (180:0:10);

\documentclass{standalone}
\usepackage{tikz}
\usetikzlibrary{decorations.markings}
\begin{document}

\begin{tikzpicture}[
tangent/.style={
    decoration={
        markings,% switch on markings
        mark=
            at position #1
            with
            {
                \coordinate (tangent point-\pgfkeysvalueof{/pgf/decoration/mark info/sequence number}) at (0pt,0pt);
                \coordinate (tangent unit vector-\pgfkeysvalueof{/pgf/decoration/mark info/sequence number}) at (1,0pt);
                \coordinate (tangent orthogonal unit vector-\pgfkeysvalueof{/pgf/decoration/mark info/sequence number}) at (0pt,1);
            }
    },
    postaction=decorate
},
use tangent/.style={
    shift=(tangent point-#1),
    x=(tangent unit vector-#1),
    y=(tangent orthogonal unit vector-#1)
},
use tangent/.default=1
]
\draw [tangent/.list={0.1,0.2,...,0.9}](0,0) arc (180:0:10);

\foreach \x [count=\xi] in {1,1,2,1,2,1,4,3,1.5}
{
\draw [red, thick,->, use tangent=\xi] (0,0) -- (0,-1*\x);
}
\end{tikzpicture}
\end{document}

Answer 2

Este es un enfoque ligeramente diferente (admito que es una solución alternativa), sin embargo, funciona bien para este escenario.

\foreach [count=\y] \x in {1,1,2,1,2,1,4,3,1.5}
{
    \path [tangent=\y/10] (0,0) arc (180:0:10);
    \draw [red, thick, ->, use tangent=1] (0,0) -- (0,-1*\x);
}   
\draw (0,0) arc (180:0:10);

Simplemente reemplace el tikzpicturecuerpo por este código.

---

Código final:

\documentclass{standalone}
\usepackage{tikz}
\usetikzlibrary{decorations.markings}

\begin{document}

    \begin{tikzpicture}[
    tangent/.style={
        decoration={
            markings,% switch on markings
            mark=
            at position #1
            with
            {
                \coordinate (tangent point-\pgfkeysvalueof{/pgf/decoration/mark info/sequence number}) at (0pt,0pt);
                \coordinate (tangent unit vector-\pgfkeysvalueof{/pgf/decoration/mark info/sequence number}) at (1,0pt);
                \coordinate (tangent orthogonal unit vector-\pgfkeysvalueof{/pgf/decoration/mark info/sequence number}) at (0pt,1);
            }
        },
        postaction=decorate
    },
    use tangent/.style={
        shift=(tangent point-#1),
        x=(tangent unit vector-#1),
        y=(tangent orthogonal unit vector-#1)
    },
    use tangent/.default=1
    ]

    \foreach [count=\y] \x in {1,1,2,1,2,1,4,3,1.5}
    {
        \path [tangent=\y/10] (0,0) arc (180:0:10);
        \draw [red, thick,->, use tangent=1] (0,0) -- (0,-1*\x);
    }   
    \draw (0,0) arc (180:0:10); 

    \end{tikzpicture}
\end{document}

Answer 3

Esto se puede hacer fácilmente con foreach. Utilizo un enfoque más simple que el tuyo. El resultado es

\documentclass[border={10}]{standalone}
\usepackage{tikz}  

\begin{document}

\def \r {8}

\begin{tikzpicture}
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\draw[very thick] (\r,0) arc (0:180:\r);

\foreach \angle / \y in {18/6, 36/7, 54/6, 72/7,90/6, 108/7,126/6,144/7,162/6}
\draw [<-, very thick,red]
   ( {  (\y)*cos(\angle)}, { (\y)*sin(\angle)} ) --
   ( {  (\r)*cos(\angle)}, { (\r)*sin(\angle)} );
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\end{tikzpicture}

\end{document}