Adding double arrows to the middle of a line with TikZ

Question

I am using tkz-euclide package and I am drawing a figure where I would like to put two arrows in the center of the line, exactly as seen in this figure:

Ideally, I may want to create a single arrow, two arrows, three arrows, etc. in the center of a line, so a generalized solution would be great.

Answer 1

Notes

• The \tkzMarkSegments[<opt>]{…} macros offer the ability to mark= with |, ||, o, s, etc.
  Refer to the tkz-euclide manual for more information (12.3 “Marquer un segment \tkzMarkSegment” and 12.4 “Marquer des segments \tkzMarkSegments”).
• I haven’t fount a way to be able to use, say, mark=>, which is the reason I provide the
• arrowMe style.
• thick is only one of many ways to make a arrow head bigger, this isn't the best, for further reference, take a look at
  • chapter 23 “Arrow Tip Library” of the Tik Z manual, and
  • Is it possible to change the size of an arrowhead in TikZ/PGF?
• Double arrows are provided by the universal > arrow or with the \pgfarrowsdeclaredouble macro.
• Triple arrow can be declared with \pgfarrowsdeclaretriple macro.
• Quadruple arrow can be declared with doubling the double arrow tip.
  With the example given you can see that the end of the arrow’s tip is actually at the specified position (here pos=.5) and not the middle of the arrow, which is the reason I prefer to use the method I described in another answer of mine, but the explained decoration doesn’t work so good with \tkz*Segment so the fallback would be to explicitly \draw the line.
• See the related question where different ways of marking with an arrow are provided:
  • TikZ-pgf directed graph: change arrow color and location
  • TikZ: How to draw an arrow in the middle of the line?

Code

\documentclass[tikz,border=2pt]{standalone}
\usepackage{tikz}
\usepackage{tkz-euclide}
\usetikzlibrary{decorations.markings,arrows}
\tikzset{
    arrowMe/.style={
        postaction=decorate,
        decoration={
            markings,
            mark=at position .5 with {\arrow[thick]{#1}}
        }
    }
}
\pgfarrowsdeclaredouble{<<s}{>>s}{stealth}{stealth}%   double stealth
\pgfarrowsdeclaretriple{<<<s}{>>>s}{stealth}{stealth}% triple stealth
\pgfarrowsdeclaredouble{<<<<s}{>>>>s}{<<s}{>>s}%    quadruple stealth
\begin{document}
\begin{tikzpicture}
    \tkzDefPoint(0,0){D}
    \tkzDefPoint(2,4){A}
    \tkzDefPoint(7,4){B}
    \tkzDefPoint(5,0){C}
    \tkzDefPoint(3.5,2){E}
    \tkzDefPoint(6,2){BC}% only to show the quadruple arrow
    \tkzLabelPoints[left](A,D)
    \tkzLabelPoints[right](B,C)
    \tkzLabelPoints[left=5pt](E)
    \tkzDrawSegments(B,D A,C)
    \tkzMarkSegments[mark=|](B,E D,E)
    \tkzMarkSegments[mark=||](A,E C,E)
    \tkzDrawSegments[arrowMe=stealth](A,B D,C)
    \tkzDrawSegments[>=stealth,arrowMe=>>](D,A C,B)
    \tkzDrawSegment[arrowMe=>>>>s](BC,E)% only to show the quadruple arrow
\end{tikzpicture}
\end{document}

Output