in parcolumns it has \z@ all over the space. I don't see it define it anywhere so I assume it is some internal command or something? I can't really make heads or tails of it though and I can't really search google for it(doesn't return anything useful)
[Tex/LaTex] What does \z@ do
latex-basemacros
Related Solutions
You are missing two very important \expandafters.
The normally used, "correct" code is:
\def\ifeq#1#2{%
\ifx#1#2\relax
\expandafter\@firstoftwo
\else
\expandafter\@secondoftwo
\fi
}
The difference to a macro which uses #3 and #4 is that the if-statement is fully processed before the first or second of the next two arguments is processed. This allows that code to e.g. look ahead using \@ifnextchar. Otherwise the \else or \fi would still be after the #3 or #4, respectively, which would break such macros. Such techniques to close the if-statement first are also important for recursive macro to not accumulate a lot of cascaded if-statements.
The macros are defined \long simply to allow for the most flexible use.
The \@firstofone macro seems to be a no-op, but actually removes the braces around the argument. It is often used in an if-statement where \@gobble is used in the other clause (both again using \expandafter).
\def\foo#1#2{%
\ifx#1#2%
\expandafter\@firstofone
\else
\expandafter\@gobble
\fi
}
\foo{\bar}{\baz}{Argument code}
For math mode this should work.
\documentclass{article}
\usepackage{xparse}
\ExplSyntaxOn
\NewDocumentCommand{\showcase}{v}
{
\texttt{#1} & \tl_rescan:nn { } { $#1$ }
}
\ExplSyntaxOff
\begin{document}
\begin{tabular}{cc|cc}
\showcase{x^{y}} & \showcase{\hat{x}, \bar{x}} \\
\showcase{x_{y}} & \showcase{f\colon X \to Y} \\
\showcase{x'} & \showcase{\sqrt{x+2}} \\
\showcase{x''_{2}} & \showcase{2 < x \leq 4} \\
\showcase{A^{1}_{2}} & \showcase{\frac{a+b}{c+d}} \\
\showcase{3\pi/4} & \showcase{\int_{0}^{1} x^{2} \,dx} \\
\showcase{x\in\Omega} & \showcase{A \cup B \subseteq C \cap D}
\end{tabular}
\end{document}
Should you want to swap the columns, so the result appears before the code, just change the definition of \showcase inverting the cells:
\NewDocumentCommand{\showcase}{v}
{
\tl_rescan:nn { } { $#1$ } & \texttt{#1}
}
Best Answer
\z@is a LaTeX “constant” that's defined to be zero. Package developers can use it to assign or test against the value0and it can also replace a length of0pt. Similar constants are\@ne(one)\tw@(two) and so on. Due to the@they can only be used in packages or between\makeatletterand\makeatother.