# split exact sequence in tikz

Is there an easy way to draw a split exact sequence in tikz cd (that is, with an arrow going from A to B, and a reverse arrow going from B to A)? There is obviously a way to do this with the full tikz, but this is a little painful...

EDIT to answer the comment, the picture should look something like this:

(just the T-> PO part, Except I would prefer the back arrow to curve less)

• Welcome to LaTeX! Welcome to TeX.SX! Could you please elaborate on what you want drawn? Perhaps find an illustration or draw one. – JP-Ellis Feb 29 '16 at 14:13
• @JP-Ellis I added an illustration, thanks! – Igor Rivin Feb 29 '16 at 14:20

There is nothing which could not be found in the tikz-cd-manual, but here you are:

% arara: pdflatex

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

\begin{document}
\begin{tikzcd}
0\arrow{r} & \mathbb{R}\arrow{r}{t}\arrow{d}{\mathcal{P}} & X\arrow{r}{\pi}\arrow{d}{s} & G\arrow{r}\arrow[equal]{d} & 0 \\
0\arrow{r} & \mathbb{T}\arrow{r}{r} & \text{PO}\arrow{r}\arrow[bend left=33]{l}{\varphi} & G\arrow{r} & 0
\end{tikzcd}
\end{document}


As you want to reduce the bending radius, I have put the label r above. If you want the look of your screenshot, just do \arrow{r}[swap]{r}!

If you want to have a bending less than 33, you will encounter this bug.

• Thanks! I actually did not see anything exactly like this in the manual (and so I was afraid of all sorts of unpleasantness). – Igor Rivin Feb 29 '16 at 14:57