I know all of the following are used for showing the absolute value:
$\lvert x \rvert$$| x |$$\mid x \mid$
I myself think that there is another one \abs; but I can't use this last one.
What is the difference between them?
[Tex/LaTex] Difference between symbols for absolute value
symbols
Related Solutions
I have been using the code below using \DeclarePairedDelimiter from the mathtools package.
Since I don't think I have a case where I don't want this to scale based on the parameter, I make use of Swap definition of starred and non-starred command so that the normal use will automatically scale, and the starred version won't:
If you want it the other way around comment out the code between \makeatother...\makeatletter.
\documentclass{article}
\usepackage{mathtools}
\DeclarePairedDelimiter\abs{\lvert}{\rvert}%
\DeclarePairedDelimiter\norm{\lVert}{\rVert}%
% Swap the definition of \abs* and \norm*, so that \abs
% and \norm resizes the size of the brackets, and the
% starred version does not.
\makeatletter
\let\oldabs\abs
\def\abs{\@ifstar{\oldabs}{\oldabs*}}
%
\let\oldnorm\norm
\def\norm{\@ifstar{\oldnorm}{\oldnorm*}}
\makeatother
\newcommand*{\Value}{\frac{1}{2}x^2}%
\begin{document}
\[\abs{\Value} \quad \norm{\Value} \qquad\text{non-starred} \]
\[\abs*{\Value} \quad \norm*{\Value} \qquad\text{starred}\qquad\]
\end{document}
No. That quote is not correct.
In Plain TeX, \le is let to \leq and \ge is let to \geq, so they are equivalent.
The LaTeX kernel contains the following lines:
\DeclareMathSymbol{\leq}{\mathrel}{symbols}{"14}
\let\le=\leq
\DeclareMathSymbol{\geq}{\mathrel}{symbols}{"15}
\let\ge=\geq
so the pairs \le,\leq, and \ge, \geq are equivalent in standard LaTeX.
As you can see, \ge and \geq are just different names for the same object (and similarly for \le and \leq). Both \ge and \geq stand for "greater than or equal to" and both \le and \leq stand for "less than or equal to".
Best Answer
You ask for the differences and here's an analysis for them.
First let's get rid of the last case:
\midis a relation symbol like=or<and TeX adds spaces around it that disqualify the command from being used for the absolute value.The other two seem good, but the first one is better as it doesn't need precautions. The fact is that
|is considered an ordinary symbol, whereas\lvertis an opening (like[) and\rvertis a closing (like]).Let's compare some cases.
You can see in the picture that
\lvertand\rvertproduces the right spacing in all cases, whereas|...|doesn't. Not to speak about\mid.Using
|would force you to inputYou can define
\absas suggested in answers to Absolute Value Symbols but I recommend not to follow the suggestion of making\leftand\rightautomatic, because it will most of the time choose a wrong size.