# xy-pic: moving start and end of bent arrow

I would like to improve the following Xy-pic drawing by putting the beginning of the arrow centered under the $x$ and its end centered under $f_u(x) u$:

\xymatrix@R=6pt{
E \ar[r]^-{f_u} & \K \ar[r]^-{h_u} & E \\
x \ar@{|->}[r] \ar@/_1.5pc/[rr]_-{\pi = h_u\circ f_u} & f_u(x) \ar@{|->}[r] & f_u(x)u
}


I read this answer: Xy-pic moving the position of an arrow but I can't understand how to apply it to my case in the \ar@/_1.5pc/[rr]_-{\pi = h_u\circ f_u} portion of code...

Any idea?

## EDIT:

The MWE before tip:

\documentclass[francais,12pt]{article}

\usepackage[french]{babel}
\usepackage[ansinew]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{amsmath, amsthm, amssymb}
%\usepackage{graphicx}
\usepackage{pb-diagram}
\usepackage[all]{xy}

\begin{document}

Try...

$\shorthandoff{;:!?} \xymatrix@R=6pt{ E \ar[r]^-{f_u} & \mathbb{K} \ar[r]^-{h_u} & E \\ x \ar@{|->}[r] \ar@(_,_)[rr]_-{\pi = h_u\circ f_u} & f_u(x) \ar@{|->}[r] & f_u(x)u }$

\end{document}

• What's wrong with my "\$" (latex)?? – biblio Feb 7 '18 at 19:27
• Please post complete-but-minimal code rather than a snippet. – Thruston Feb 7 '18 at 20:48
• We don't have TeX interpretation on this site -- too often we talk about the TeX source rather than the ouput. – Thruston Feb 7 '18 at 20:48

You can do this by changing the arrow bend modifier on the [rr] arrow.

(See p.42 in the reference manual ).

\documentclass[border=0.5]{standalone}
\usepackage[all]{xy}
\begin{document}
\xymatrix@R=6pt{
E \ar[r]^-{f_u} & K \ar[r]^-{h_u} & E \\
x \ar@{|->}[r] \ar@(_,_)[rr]_-{\pi = h_u\circ f_u} & f_u(x) \ar@{|->}[r] & f_u(x)u
}
\end{document}


I'm not sure it looks any better though:

If you call \usepackage[all,cmtip]{xy}, the diagram becomes

• Without the cmtip option, tips on bent arrows are awful; slightly less so on straight arrows. – egreg Feb 8 '18 at 8:28
• OK, thanks, it's almost perfect, except that the bend is to large (I chose 1.5pc after several tries... ;)). How can I mix the bending control and this modifier, if possible? Otherwise, how can I change the bend with only the modifier? – biblio Feb 8 '18 at 14:19
• @egreg: how can I call this option? Where do I have to put it (e.g. to which package is it related?) ? – biblio Feb 8 '18 at 14:20
• @biblio \usepackage[all,cmtip]{xy} – egreg Feb 8 '18 at 14:20
• OK, but I don't see any difference (what? it's not magical??), so I guess there are commands to add somewhere...? – biblio Feb 8 '18 at 14:22

An alternative with tikz-cd:

\documentclass{article}
\usepackage{tikz-cd}

\begin{document}

\begin{tikzcd}[row sep=6pt]
E \arrow[r,"f_u"] & K \arrow[r,"h_u"] & E \\
x \arrow[r,mapsto]
\arrow[rr,swap,out=-45,in=-135,"\pi = h_u\circ f_u"] &
f_u(x) \arrow[r,mapsto] & f_u(x)u
\end{tikzcd}

\end{document}


• Thnks but it doesn't answer my question which is: how to put start and end of arrow centered under the scalar and its image? If I change the angles, the start and end move closer and it's quite the same my first try without the (,) modifier... Or maybe I was wrong somewhere? – biblio Feb 8 '18 at 15:08
• By the way, I can't see the image, I have a "enter image description here", and when I click on the link, the server answers "unreachable"... Any explanation? – biblio Feb 8 '18 at 15:10
• @biblio Apparently you can't momentarily reach Imgur, try again later. – egreg Feb 8 '18 at 15:16
• OK, it seems it depends on the computer... – biblio Feb 9 '18 at 19:26