[doc] Replace \diameter representing radius with \r

[muzimuzhi]

1. Replace -to with -To in Section 3. Tutorial: A Petri-Net for Hagen
   Arrow tip to is from deprecated library arrows, which is not
   documented in latest pgfmanual anymore. Use undocumented setting
   in tutorial sections will confuse careful new users, see Archive old manuals? #903.
   Hence I replace -to with ->.

2. Replace \diameter used in ... circle (\diameter) with \r.
   Note: Although ... circle (<radius>) is an old syntax (mentioned
   in the last two paragraphs of pgfmanual 3.1.5b, sec. 14.6), I didn't
   replace it with ... circle[radius=<radius>].
   A simple grep shows there are ~200 usages of ... circle (<radius>)
   throughout the pgfmanual, and since this syntax is more convenient,
   I don't have a strong opinion to replace all of them.

[muzimuzhi]

@AndreC75

there is still -to in page 1076 \begin{pgfpicture} \begin{pgfscope} { \pgfsetarrows{-to} \pgfpathmoveto{\pgfpointorigin}\pgfpathlineto{\pgfpoint{2ex}{2ex}} \pgfusepath{stroke} } \pgfpathmoveto{\pgfpoint{3ex}{0ex}}\pgfpathlineto{\pgfpoint{5ex}{2ex}} \pgfusepath{stroke} \end{pgfscope} \pgfpathmoveto{\pgfpoint{6ex}{0ex}}\pgfpathlineto{\pgfpoint{8ex}{2ex}} \pgfusepath{stroke} \end{pgfpicture}
#903 (comment)

What you found is already handled in the second commit of current pr, b983e77.

[Mo-Gul]

To 1.
Actually the to arrow tip was/is not an arrow tip of the arrows library, but is a predefined arrow tip. See #746 (comment).

[muzimuzhi]

To 1.
Actually this to was/is not an arrow of the arrows library, but is a predefined arrow tip. See #746 (comment).

Ah yes. I should have found this by myself. I've opened #906 to discuss this issue. After #906 get resolved, the first two commits of current pr are then avoidable.

[AndreC75]

@Mo-Gul @muzimuzhi I noticed that -To (with a capital T) is also an arrow. Manual 3.1.5b talks about this on page 207.

[Mo-Gul]

@AndreC75, To is an arrow tip from the arrows.meta library, as can be seen on the corresponding manual section 16.5 on page 212.

[AndreC75]

@muzimuzhi @Mo-Gul

the arrows -to, -To are the same, so in the manual it seems better to replace -to by -To

`\documentclass[tikz,border=5mm]{standalone}

\begin{document}

\begin{tikzpicture}[nodes={font=\small\ttfamily, black, right}]

\draw[-to] (0,0)--(2,0)node{arrow "-to"};

\begin{scope}[yshift=-1cm]
\draw[-To] (0,0)--(2,0)node{arrow "-To"};
\end{scope}

\begin{scope}[yshift=-2cm]
\draw[->] (0,0)--(2,0) node{arrow "->"};
\end{scope}
\end{tikzpicture}

\end{document}`

[muzimuzhi]

@AndreC75

the arrows -to, -To are the same,

They are the same by default, but are different if arrows.meta is loaded, since at that time To is redefined to Computer Modern Rightarrow.

pgf/tex/generic/pgf/basiclayer/pgfcorearrows.code.tex

Line 1168 in bbe2b56

\pgfkeys{To /.tip = to}

pgf/tex/generic/pgf/libraries/pgflibraryarrows.meta.code.tex

Line 1598 in bbe2b56

To /.tip = {Computer Modern Rightarrow},

And > is always the same as To.

pgf/tex/generic/pgf/basiclayer/pgfcorearrows.code.tex

Line 1070 in bbe2b56

<-> /.tip = {To},

Also see this example.

\documentclass{article}
\usepackage{graphicx}
\usepackage{tikz}

\begin{document}
\tikzset{nodes={font=\ttfamily\tiny}}

Default\par
% Default arrow tips like `to` does not respect arrow options like `scale`, hence I have to use `\scalebox` to enlarge it.
\scalebox{3}{\begin{tikzpicture}
  \foreach \i[count=\xi] in {>, to, To} {
    \draw[-\i, yshift=\xi*-.3cm] (0, 0) -- (1, 0) node[right] {\i};
  }
\end{tikzpicture}}

\usetikzlibrary{arrows.meta}

With \texttt{arrows.meta} loaded\par
\scalebox{3}{\begin{tikzpicture}
  \foreach \i[count=\xi] in {>, to, Classical TikZ Rightarrow, To, Computer Modern Rightarrow} {
    \draw[-\i, yshift=\xi*-.3cm] (0, 0) -- (1, 0) node[right] {\i};
  }
\end{tikzpicture}}
\end{document}

so in the manual it seems better to replace -to by -To

I agree. Though using > in tutorial sections of pgfmanual seems more gentle for new users.

[AndreC75]

@muzimuzhi The tutorials are also an opportunity to discover new features. I prefer to put -To quite to indicate the section where it is defined or indicate that it is an arrow. This can motivate to go see the predefined arrows.

[muzimuzhi]

Changes in force pushed commits:

• -to is now replaced by -To, in Section 3. Tutorial: A Petri-Net for Hagen.
• Change that replaced \pgfsetarrows{-to} by \pgfsetarrows{->} is reverted, since to is one of default arrow tips and not deprecated.

[muzimuzhi]

@hmenke Has added a 0e9f8a6 to replace -to with ->.

I'm OK with either -> or -To, but there is a small flaw in using ->. (Sorry I've found it yesterday but didn't mention it in my previous #905 (comment).)

• default style of > is used through out Subsection 3.12 Adding the Snaked Line and Multi-Line Text, hence here -> is equivalent to -To (pgfmanual loads arrows.meta).
  

• modified style of > is used in complete example in beginning and ending of Section 3. Tutorial: A Petri-Net for Hagen, where > is redefined to >={Stealth[round]}.
  

Hence there is a gap, not sure if that would confuse new users.

[AndreC75]

@muzimuzhi @hmenke In my opinion, since in the original there is a predefined arrow -to, you have to keep a predefined arrow -To and not a shortcut -> that can be redefined. Thus, the example retains the original idea of Till Tantau.

[hmenke]

Please resolve the merge conflicts.

[muzimuzhi]

@hmenke What's your (current) opinion about arrow tip staff?

[hmenke]

I've already replaced -to by -> in 0e9f8a6 and I will leave it at that. Of course, bikeshedding the manual and trying to come up with the best formulations is easy but also completely irrelevant because nobody actually reads the manual.

[muzimuzhi]

OK. e671fd1, which changed arrow tips, is reverted and the whole branch is rebased.