As an example, here is s_1, without a height set.
\begin{center}
\begin{tikzpicture}
\pic[
braid/.cd,
%height = 1cm,
name prefix=braid,
] {braid={s_1}};
\end{tikzpicture}
\end{center}

by uncommenting out the height line, we get s_^{-1}.

Hi Andrew!

I'm having problems getting your braids package to work for me. I have downloaded the package from CTAN

http://mirrors.ctan.org/graphics/pgf/contrib/braids.zip

unzipped it and entered the braids folder, run pdflatex braids_code.tex twice and then pdflatex braids.tex and I get the following error message

! Undefined control sequence.
...\l__braid_tmpb_tl }\str_case_e:nnTF
{\l__braid_tmpa_str }{{}{...
l.62 ...{17} s_2-s{13}-s_{16} s_1-s_{12}-s_{15}}}
;

Could you help me figure out what's not working?

Thanks!
Paul

An annular braid is one that wraps round from one side to the next, so the first and last strands can cross.

First thoughts on implementation:

Allow for specifying a "first strand" and "last strand", then any strands beyond that are clipped out but can still be used in crossings, with strand styles wrapped so that strand 1 and strand n+1 have the same style, and something similar about crossings so that if strand 0 and strand 1 cross then so do strands n and n+1.

This is not an issue but a feature request.

Is it possible to have crossings of the type generated using the knots package for the braids package? By that I mean the following.

This is a crossing using the braids package.

And this is a crossing using the knots package.

The crossing using the knots package looks as if the upper strand has an invisible opaque tube surrounding it which covers the lower strand. The cuts to the lower strand are thus at an angle to the strand direction, while the cuts are always perpendicular to the lower strand in the braids package. I wanted to ask/request if there is a possibility of the knots type cuts in the braids package.

There are some missing character warnings with the new tikz library. I know they can be ignored, but they make it harder to find all the other problems with my tex documents :/

Example input:

\documentclass{minimal}

\usepackage{tikz}
\usetikzlibrary{
  braids,
  arrows.meta
}

\begin{document}

\begin{tikzpicture}[ultra thick]
\pic[
  rotate=90,
  braid/.cd,
  strand 1/.style={red},
  height=1cm,
  width=1cm,
] (braid) at (1,2) {braid={s_1 s_2}};
\end{tikzpicture}

\end{document}

Output snippet:

[Loading MPS to PDF converter (version 2006.09.02).]
) (/usr/share/texlive/texmf-dist/tex/latex/epstopdf-pkg/epstopdf-base.sty
(/usr/share/texlive/texmf-dist/tex/latex/latexconfig/epstopdf-sys.cfg))
Missing character: There is no c in font nullfont!
Missing character: There is no o in font nullfont!
Missing character: There is no d in font nullfont!
Missing character: There is no e in font nullfont!
Missing character: There is no = in font nullfont!
[1] (./braid_pic.aux) )
Output written on braid_pic.pdf (1 page, 1341 bytes).

(continuing the discussion we started at #2, but as a separate issue)

Here are some more specific suggestions I had for the documentation of the tikz library. I could definitely do some of these, if you like (and others, with a little help explaining the parts I don't know). But I'm happy to defer to your judgement and let you handle them (or not) as you prefer.

1. Section 2.2, line 4 mentions name prefix. Probably this should appear as one of the keys in the left margin, somewhere. It's not in the /tikz/braid/ namespace though, so maybe it should be listed before the 2.1 section break? (Update: oh, this is a general tikz thing that I didn't know about. Maybe a link to the tikz documentation for it?)
2. Section 2.2, paragraph 2, the last sentence says "This node is not actually rendered, but its anchors can be used..." Do you mean the node doesn't really exist, or just that it's not drawn? What are some examples of the anchors that can be used? I expected something like \node at (braidname.south) {X}; to mark the bottom center of the braid, but it doesn't seem to work. I include name prefix=braidname, but I get Package pgf Error: No shape named 'braidname' is known.
3. braid/.cd appears in the examples on page 6, but doesn't seem to be documented. (Update: after some testing, this appears to be a tikz change directory command!)
4. page 3, in the last paragraph before item number 3, says "Replacing the floor pic will change how it is drawn". Does this mean one can draw floor shapes that are not rectangles? E.g., an oval?
5. Related to the above, how can one draw a rectangular floor where only one of the edges is drawn? Is this possible?
6. These explanations of braid/every floor and braid/floor <n> might be better placed on page 4, where those keys appear in the left margin. Then, the description in item number 2 on page 2 could be shortened with a reference to further details below.

I made a little example in this commit illustrating what I know about the above items, with several notes about how it might be improved. Here is a link to the pdf output.