Merging Arrows to Show Implications in Tikz-CD

Question

I'm trying to create a diagram with logical implications between various propositions, and some of them are conjunctions. Suppose I want to show this:

 A => C
 A&B => D

the best I can get so far is this, but there's still some space that I can't get rid of:

$$\begin{tikzcd}
     a\arrow[d,Rightarrow]
      \arrow[dr,Rightarrow,""{name=A}] 
   & b\arrow[to=A,Rightarrow,dash] \\
   c & d
\end{tikzcd}$$

I feel this must be a common problem and probably I'm missing something obvious.

In general you should post a complete "Minimal Working Example" (MWE) that starts with \documentclass, includes all relevant \usepackage commands, ends with \end{document} and compiles without errors, even if it does not produce your desired output. Also, it's usually best to use \[..\] instead of $$..$$. — Sandy G, Oct 08 '20 at 20:18

score 5 · Accepted Answer · answered Oct 08 '20 at 20:05

5

This is a bit of a hack, since the placement and length of the equals arrow was found by trial and error. For a different diagram you'd have to make adjustments.

\documentclass{article}
\usepackage{tikz-cd}
\begin{document}
\begin{tikzcd}
     a\arrow[d,Rightarrow]
      \arrow[dr,Rightarrow,""{name=A, xshift=4.85pt}] 
   & b\arrow[to=A, equals, shorten >=-8.75pt] \
   c & d
\end{tikzcd}
\end{document}

The shorten > key can be used with a negative value to increase the length of the equals arrow. Note the required space between shorten and >.

answered Oct 08 '20 at 20:05

Sandy G

42,558

I had not understood the request of the user. +1 – Sebastiano Oct 08 '20 at 20:09
1

@Sebastiano, I didn't understand either until I saw the comment on your post. I was going to suggest the same thing you did. – Sandy G Oct 08 '20 at 20:11
Thanks Sandy, that's what I wanted to get. Thanks also for the reference on using \[ \] over $$. – Tom Cunningham Oct 08 '20 at 21:55

Merging Arrows to Show Implications in Tikz-CD

1 Answers1