\documentclass{article}
\usepackage{tikz}

\begin{document}
\begin{tikzpicture}
\node (A) {A};
\node[right of=A] (B) {B};
\draw[->] (A.south) edge[out=-90,in=-90] (B.south);
\draw[->] (A.north) -- (B.north);
\end{tikzpicture}
\end{document}

Why does the first \draw give me a double headed arrow and the second not? I'm sure I've used the first's syntax before with a single headed arrow. Has something changed?

@AlanMunn I don't know, but I get an arrow head on both sides also in old tex system., e.g. tl14.

quack

@PauloCereda breakfast

@PauloCereda quack

@DavidCarlisle oh no

@JosephWright ooh quack

Greetings from my first day at work!

@Skillmonlikestopanswers.xyz :)

@AlanMunn why edge instead of to?

@AlanMunn if you use \path[->] (A.south) edge[out=-90,in=-90] (B.south); it works --- albeit after re-reading the tikz manual (17.12, around page 257) I do not know why...

@AlanMunn Also \draw (A.south) edge[->, out=-90,in=-90] (B.south); works...

@Sebastiano don't think there was anything wrong with your deleted mathrfs suggestion

@Sebastiano My comment to your answer to tex.stackexchange.com/questions/536297 was more my belief rather than a statement that should be taken for granted. I would welcome it if you agree or disagree with my comment – of course, if you have something to say beyond what Ulrike said.

@Sebastiano Even if you don't know better, you can even choose to restore your answer to that others can comment on it.

archive.org/details/texbook00dona

From Twitter

@JosephWright oh my

@JosephWright $3? :-O I bought mine while serving on a ship in Italian Navy, in a very big library near Harvard in Boston (my ship was going around North Atlantic shores). I can't remember the price, but it was quite expensive for me at the time...

@Rmano Well this is a 14-day rental

@JosephWright Ah! Didn't notice it. Reasonable!

@JosephWright 14 days are clearly not enough ;-)

@UlrikeFischer Well no, but my TeXbook is at work, and I can't go in without special permission

@JosephWright ;-) I guess "saving my texbook" wouldn't count as excuse.

@UlrikeFischer Er, no, I think not: I might get away with 'There are some textbooks which are essential'

@JosephWright have fun reading the sources!

@Skillmonlikestopanswers.xyz It's what I usually do ...

@Skillmonlikestopanswers.xyz Most of the time I use TeX by Topic

@Rmano Yes, this is what I used, but weirdly I have other arrows with the other syntax that seem to work.

@Skillmonlikestopanswers.xyz Not sure. The document is kind of old, so it might reflect my knowledge state at the time (which may not have changed much... :) )

@UlrikeFischer you only need read appendix D, 14 days should be plenty

@DavidCarlisle 14 days are only enough if you have a devious mind.

@DavidCarlisle a devious mind is a necessary but not a sufficient condition.

@AlanMunn There have been some questions on the site about double arrows with edge I think. If I remember correctly, edge inserts a second path, so you get one arrow tip on the edge, and one on the original path, which ends up on the first coordinate, and there is no line from/to it. Try \draw[->] (A.south) edge[red,out=-90,in=-90] (B.south); and look at the first arrow tip.

@AlanMunn But perhaps you knew that. I don't know why it only happens in some cases for you.

@TorbjørnT. No I didn't know that. But here's a bit of code from the same document that works correctly, with the same syntax:

\documentclass{article}
\usepackage{tikz}
\usepackage{tikz-qtree,tikz-qtree-compat}
\newcommand*\1{$'$}
\newcommand\trace[1]{<#1>}

\begin{document}
\begin{tikzpicture}[baseline]\Tree [.TP [.\node (J3){DP\\John}; ] [.T\1 [.T\\PRES ]  [.VP [.V\\seem ] [.TP [.\node (J2) {DP\\\trace{John}}; ] [.T\1 [.T\\to ] [.VP [.\node (J1){DP\\\trace{John}}; ] [.V\1 [.V\\like ] [.DP\\Mary ]]]]]]]]]]
\draw[->] (J1) edge[red,out=-90,in=-90] (J2);
\draw[->] (J2) edge[red,out=-90,in=-90] (J3);\end{tikzpicture}
\end{document}

And the red colours everything.

@AlanMunn Seems there's a difference between using just a node name and a node anchor.

@AlanMunn tex.stackexchange.com/questions/82326/… tex.stackexchange.com/questions/15567/…

@TorbjørnT. Ah, yes, that does seem to be it. It seems like this is the explanation. tex.stackexchange.com/q/15567/2693

@TorbjørnT Great minds... :)

@AlanMunn Indeed.

@TorbjørnT. A very nice explanation too. (Not surprising, given that it was by Jake.)

No April fools needed. The world itself is an April fool.

@DavidCarlisle what is the easiest way to remove a potential slash at the begin of a value?

@UlrikeFischer you mean a catcode 12 / ?

@DavidCarlisle yes. I have inside a macro /Source but need Source there (it is about the embedfile issue).

@UlrikeFischer \def\zz#1{\if/#1\else#1\fi}\zz /Source ?

@DavidCarlisle and when it is already inside a command?

@UlrikeFischer a few \expandafter never hurts

@DavidCarlisle I have added a fix, I'm not sure if it is really the best but it should work.

@UlrikeFischer which reminds me did your release the font packages?

vimeo.com/403032474

@DavidCarlisle no not yet, I had it on my list for today but didn't manage to find the time. I will try to do it after dinner.

@UlrikeFischer oh no

oh wait, it's a safe dinner, not @DavidCarlisle's dinner trigger. :)

@DavidCarlisle I'm so tired that it seemed to me that I had made a mistake or the user had complained about something. I have a lot of work for the school and honestly I didn't understand the user's comment. So I deleted everything.

@Sebastiano your answer was fine. The user was simply picky.

@Just_A_Man In all honesty, I did not understand anything you had commented and I removed my answer. It probably wasn't what you asked for. I help myself a lot with images. For me, there are no problems of any kind.

@CarLaTeX A heartfelt embrace to all of northern Italy from Sicilia. "tenete duro mi raccomando". Here in Sicily the virus is contained but if the situation worsens it will be a disaster.

@UlrikeFischer Ulrike I tell you with my heart in my hands I'm on tilt. I hadn't understood anything and I eliminated my answer. I also thought I had made a mistake and I restored my answer by invitation.

It's almost ten hours on the computer for distance learning and I can't satisfy my students who are happy with me.

I have closed the chat and I didn't even noticed. Sorry, everyone, if I make or will make mistakes.

@UlrikeFischer Don't worry :-)

@Sebastiano Hi Sebastiano, it seems that the situation is getting better here, let's hope the virus doesn't like hot weather!

@CarLaTeX That's for sure, the only thing we know for sure is that the coronavirus is very aggressive and we don't know how it evolves. There is no history of this type of virus that created the pandemic.

@Sebastiano Yes, lockdown is the only defence

@CarLaTeX Here where I live, everyone's around with cars and mopeds with cloth masks. Most masks are homemade. There's less traffic at night. Sicily has always been particular.

@Sebastiano Very few people around in Milan only for buying food

@CarLaTeX This place looks like war. I only go shopping when I can late at night. In the morning is a big problem with the queue of people who fill shopping carts and stay inside for many minutes and don't think there are so many people waiting for them to come out.

@Sebastiano I haven't had big problems with the queues but there are many shops and supermarkets near my house, so people have more possibilities

@CarLaTeX Here they make the raid of the food:-)

@Sebastiano Here, too, of disinfectants and toilet paper :)

@CarLaTeX :-)

@Sebastiano I apologize if I was unintelligible. In any case, you might consider restoring the code and leaving commenting to more experienced folks. Here at TeX.SE, folks rarely downvote, and I interpret what Ulrike and David said as an apperication of your answer.

@barbarabeeton I just learned about another way of handling the social-distancing-credo:

@UlrichDiez -- That looks rather like fun! Where can one try this out?

@barbarabeeton I'm sorry, I have no idea: We have a public swimming pool in my village where you could probably do this in the summer-time but currently all these things are closed. Friend of mine drew my attention towards these zorbing balls and suggested to do it in the supermarket - would be some sort of macro-pinball ;-)

@UlrichDiez -- Too bad. But wouldn't this make picking things off supermarket shelves rather problematic?

@Sebastiano You are humble and generous... that is my wish. – this should be a chat message rather than a comment. In any case, I am the most humble person on earth. As for generousity, +1 :-).

@Just_A_Man Everyone but everyone knows very well that I can't write in English and I use the translator. You can ask anyone. Mine was a wish for peace and quiet. My best regards.

@DavidCarlisle packages uploaded ...

@UlrikeFischer thanks

@DavidCarlisle lets hope that it pass and that I didn't break something ;-)

@UlrikeFischer it's Ok we can blame you if it breaks

@Sebastiano I see. I beg your pardon.

@DavidCarlisle that's reassuring; -)

@UlrikeFischer I try give encouragement where I can.

@Just_A_Man Don't worry... and try to rest peacefully. I'm busy loading my students' video lectures and putting them in their place. My regards.