Passing values to a command

Question

I am new to Tikz and have been largely following the PGFManual to learn about how to use it correctly. The PGFManual shows examples of using foreach but they do not show how to pass it to a command. The code I am writing populates space with tetrahedra to define a pyrochlore lattice. I declare commands to draw a tetrahedron given a specific coordinate.

\newcommand{\tetra}[4]{
    \coordinate (A#1) at (#2+0.00,#3+0.00,#4+0.00);
    \coordinate (B#1) at (#2+0.00,#3+0.25,#4+0.25);
    \coordinate (C#1) at (#2+0.25,#3+0.00,#4+0.25);
    \coordinate (D#1) at (#2+0.25,#3+0.25,#4+0.00);
}

\newcommand{\drawtetra}[1]{
    \draw[lf line, opacity=1] (A#1)--(B#1)--(C#1)--cycle;
    \draw[df line, opacity=1] (A#1)--(B#1)--(D#1)--cycle;
}

and then call them in the document to print out my desired tetrahedra

\tetra{1}{0.00}{0.00}{0.00}
\tetra{2}{0.00}{0.50}{0.50}
\tetra{3}{0.50}{0.00}{0.50}
\tetra{4}{0.50}{0.50}{0.00}

\drawtetra{1}
\drawtetra{2}
\drawtetra{3}
\drawtetra{4}

I would like to automate the process by doing something like

foreach \i in {1,...,4}
    \drawtetra{\i}

This gives a slew of errors that mostly have to do with endcsname

I have not found any solution for this online although the closest relation I could find used pgfkeys unfortunately I was unable to relate it back to my own program. Any help would be appreciated. The complete code to generate the image is given below:

\documentclass{minimal}
\usepackage{tikz}
\usepackage{tikz-3dplot} %mentioned by Kevin C in comments
\usetikzlibrary{arrows}  %mentioned by Kevin C in comments

\newcommand{\tetra}[4]{
  \coordinate (A#1) at (#2+0.00,#3+0.00,#4+0.00);
  \coordinate (B#1) at (#2+0.00,#3+0.25,#4+0.25);
  \coordinate (C#1) at (#2+0.25,#3+0.00,#4+0.25);
  \coordinate (D#1) at (#2+0.25,#3+0.25,#4+0.00);
}

\newcommand{\drawtetra}[1]{
  \draw[lf line, opacity=1] (A#1)--(B#1)--(C#1)--cycle;
  \draw[df line, opacity=1] (A#1)--(B#1)--(D#1)--cycle;
}

\begin{document}
  \tdplotsetmaincoords{110}{70}
  \begin{tikzpicture}[
    scale = 12,
    axis/.style={very thick, ->, >=stealth'},
    df line/.style={thick, fill=darkgray!60, opacity=1},  %darkface
    lf line/.style={thick, fill=gray!30, opacity=1},      %lightface
    tdplot_main_coords
    ]

    \draw[axis] (0,0,0) -- (0,0,1);
    \draw[axis] (0,0,0) -- (0,1,0);
    \draw[axis] (0,0,0) -- (1,0,0);

    \tetra{1}{0.00}{0.00}{0.00}
    \tetra{2}{0.00}{0.50}{0.50}
    \tetra{3}{0.50}{0.00}{0.50}
    \tetra{4}{0.50}{0.50}{0.00}

    \drawtetra{1}
    \drawtetra{2}
    \drawtetra{3}
    \drawtetra{4}
  \end{tikzpicture}
\end{document}

Answer 1

You were just missing a semicolon. Semicolons are very important in TikZ. In fact, one could say that TikZ is less like LaTeX and more like C or Java in this respect. The following works:

\foreach \i in {1,...,4} 
  \drawtetra\i;

You could alternately use a group, then you don't need the semicolon.

\foreach \i in {1,...,4} { 
  \drawtetra\i
}