How to achieve extensible double-harpoons in the style of the \xleftrightharpoons family of arrows from mathtools, but with both harpoons pointing in the same direction?
Preferably without Tikz.
[Tex/LaTex] Extensible \rightrightharpoons and \leftleftharpoons
arrowsmathabxmathtools
Related Solutions
That is due to the fact that you are adding the final coordinate. They should not be there. Simply change the lines to:
\draw[->,>=stealth',semithick] (150:1.2cm) arc[radius=1.2, start angle=150, end angle=210];
\draw[->,>=stealth',semithick] (-30:1.2cm) arc[radius=1.2, start angle=-30, end angle=30];
This problem arises in far simpler situations as well, it is not inherent to the curve. Consider for example \draw[->] (0,0) -- (2,0) (2,0); which will give an upward pointing arrow on the end of a horizontal line. Basically the new coordinate begins a new path segment and only the last segment of the path is given the arrowtip.
The following example defines \xtwoheadrightarrow and \xtwoheadleftarrow similar to the definitions of \xrightarrow and \xleftarrow:
\documentclass{article}
\usepackage{amssymb}
\usepackage{amsmath}
\makeatletter
\providecommand*{\twoheadrightarrowfill@}{%
\arrowfill@\relbar\relbar\twoheadrightarrow
}
\providecommand*{\twoheadleftarrowfill@}{%
\arrowfill@\twoheadleftarrow\relbar\relbar
}
\providecommand*{\xtwoheadrightarrow}[2][]{%
\ext@arrow 0579\twoheadrightarrowfill@{#1}{#2}%
}
\providecommand*{\xtwoheadleftarrow}[2][]{%
\ext@arrow 5097\twoheadleftarrowfill@{#1}{#2}%
}
\makeatother
\begin{document}
\[
A \xrightarrow[under]{over} B
\xtwoheadrightarrow[under]{over} C
\xtwoheadleftarrow[under]{over} D
\]
\end{document}
The case \rightrightarrows/\leftleftarrows is much more complicate. Before there is a symbol \relbar that is used for the extensible part of the arrow. But there is no symbol for the double line case. Thus the vertical positions of the lines and their thickness is not known. The following example defines \relrelbar for this purpose that is composed of \relbar lowered and raised by the amount given in macro \relrelbarsep. Therefore this macro needs to be redefined for a different font. The example uses the AMS fonts:
\documentclass{article}
\usepackage{amssymb}
\usepackage{amsmath}
\makeatletter
\newcommand*{\relrelbarsep}{.386ex}
\newcommand*{\relrelbar}{%
\mathrel{%
\mathpalette\@relrelbar\relrelbarsep
}%
}
\newcommand*{\@relrelbar}[2]{%
\raise#2\hbox to 0pt{$\m@th#1\relbar$\hss}%
\lower#2\hbox{$\m@th#1\relbar$}%
}
\providecommand*{\rightrightarrowsfill@}{%
\arrowfill@\relrelbar\relrelbar\rightrightarrows
}
\providecommand*{\leftleftarrowsfill@}{%
\arrowfill@\leftleftarrows\relrelbar\relrelbar
}
\providecommand*{\xrightrightarrows}[2][]{%
\ext@arrow 0359\rightrightarrowsfill@{#1}{#2}%
}
\providecommand*{\xleftleftarrows}[2][]{%
\ext@arrow 3095\leftleftarrowsfill@{#1}{#2}%
}
\makeatother
\begin{document}
\[
A \xrightrightarrows[under]{over} B
\xleftleftarrows[under]{over} C
\]
\end{document}
The numbers 0579, ... are four arguments for \ext@arrow that is defined by package amsmath:
\def\ext@arrow#1#2#3#4#5#6#7{%
\mathrel{\mathop{%
\setbox\z@\hbox{#5\displaystyle}%
\setbox\tw@\vbox{\m@th
\hbox{$\scriptstyle\mkern#3mu{#6}\mkern#4mu$}%
\hbox{$\scriptstyle\mkern#3mu{#7}\mkern#4mu$}%
\copy\z@
}%
\hbox to\wd\tw@{\unhbox\z@}}%
\limits
\@ifnotempty{#7}{^{\if0#1\else\mkern#1mu\fi
#7\if0#2\else\mkern#2mu\fi}}%
\@ifnotempty{#6}{_{\if0#1\else\mkern#1mu\fi
#6\if0#2\else\mkern#2mu\fi}}}%
}
Some remarks:
- The width of box
\tw@contains the maximal width of the text below. above and the symbol without text. - The latter two numbers specify the margins for the texts in the measurement phase.
- The first two numbers specify the margins for the texts that is finally set and allows to insert some asymmetry of the horizontal placement because of the arrows.
Best Answer
Something like this? A quick and dirty method...
Explanation:
Give the text to be
harpoonedas 2nd argument, in the first optional you can reduce the vertical spacing between the up and the down harpoon. If omitted, a default value of-10ptis used. This could be changed in command definition or when appropiate during usage of the command.