How to make the arrows longer

Question

For years and years I have been using longmapsto and longrightarrow and their brothers and sisters.
On this site, I found the following commands to obtain arrows for surjections and injections:
newcommand{surj}{mathrel{mathrel{mathrlap{relbarjoinrelrightarrow}mkern1murightarrow}}} and
newcommand{inj}{lhookjoinrellongrightarrow}.
However, I am not satisfied about the length of the arrows, I think they are too short.
This is an excerpt from a syllabus by the French mathematician Michèle Audin. I very much like the length of here arrows.

Is it possible to have variants of the above four with length adapted in this way? Is it also possible to have arrows of this length and stackrel{}{} being compatible with it?

egreg · Answer

You can keep adding joinrelrelbar until you get the desired length.
But don't.
documentclass{article}
usepackage{amsmath}

DeclareRobustCommand{loongrightarrow}{%
  DOTSBrelbarjoinrelrelbarjoinrelrightarrow
}
DeclareRobustCommand{loongmapsto}{DOTSBmapstocharloongrightarrow}

DeclareRobustCommand{looongrightarrow}{%
  DOTSBrelbarjoinrelrelbarjoinrelrelbarjoinrelrightarrow
}
DeclareRobustCommand{looongmapsto}{DOTSBmapstocharlooongrightarrow}

begin{document}

begin{gather}
begin{aligned}[t]
varphicolon
mathcal{O}(U) &rightarrow mathcal{O}(D) 
f              &mapsto     f|_D
end{aligned}tag{good}

begin{aligned}[t]
varphicolon
mathcal{O}(U) &longrightarrow mathcal{O}(D) 
f              &longmapsto     f|_D
end{aligned}tag{bad}

begin{aligned}[t]
varphicolon
mathcal{O}(U) &loongrightarrow mathcal{O}(D) 
f              &loongmapsto     f|_D
end{aligned}tag{worse}

begin{aligned}[t]
varphicolon
mathcal{O}(U) &looongrightarrow mathcal{O}(D) 
f              &looongmapsto     f|_D
end{aligned}tag{ugly}
end{gather}

end{document}

I added random tags if you want to refer to the arrows when discussing them. They have no connection with my actual feelings about them. ?

How to make the arrows longer

One Answer

Add your own answers!

Ask a Question