Math & Science ⇒ custom stackrel command with proper line/equation placement

[evencoil]

I would like to make a custom command that does
\stackrel{d}{\rightarrow}
when inside an equation, but does
\rightarrow_{d}
when (in mathmode) in a paragraph. (In order to avoid spreading lines in paragraphs.)

I know how to make very simple custom commands, but this is a step beyond my knowledge. Can anyone give me a hint of how I would go about doing this? Thanks.

[localghost]

There is a command which makes LaTeX not to regard the height of the box containing your operator. Additionally you should decrease the size of the upper symbol not to make it look too bad in the line.

Code: Select all

$x\smash{\stackrel{\scriptscriptstyle d}{\rightarrow}}y$

Best regards
Thorsten¹

[evencoil]

thank you, that works well for stopping the line-spreading and I think I might use that, although its not quite what I was looking for...

My idea was more along the line of how \lim works. If I use \lim_{n \rightarrow \infty} in a paragraph then the "n \rightarrow \infty" part ends up on the lower right of "lim" rather than below "lim" as it would if I used the command inside an equation environment. Do you know what the logic is that creates that and how I could apply it to this problem?

[phi]

Math atoms of class 1 take limits when inserted in display style:

Code: Select all

\documentclass{article}

\usepackage{amsmath}

\newcommand*\test{\mathop\rightarrow^x}


\begin{document}

$a \test b$

\begin{align*}
	a \test b
\end{align*}

\end{document}

[evencoil]

so now i'm being quite picky, but this is partly as an interest in learning TeX better. In that one the expression appearing in the paragraph is superscripted, whereas I would prefer it to be subscripted. This seems to require some additional logic. I was trying something like this using the ifthen package:

Code: Select all

\documentclass{article}

\usepackage{amsmath, ifthen}

\newcommand*\test{\ifthenelse{\boolean{???}}{\mathop\rightarrow^x}{\mathop\rightarrow_{x}}}

\begin{document}

$a \test b$

\begin{align*}
   a \test b
\end{align*}

\end{document}

except I can't find a TeX boolean for paragraph versus equation (there's one for mmode but that treats paragraphs and equations the same).

[phi]

Then you need to distinguish between the for math styles using \mathchoice:

Code: Select all

\documentclass{article}

\usepackage{amsmath}

\newcommand*\testA{\mathop{\mkern0mu\rightarrow}^x}
\newcommand*\testB{\mathchoice{\stackrel x\rightarrow}{\rightarrow_x}{\rightarrow_x}{\rightarrow_x}}


\begin{document}

$a \testA b \testB c$

\begin{align*}
	&a \testA b \testB c \\
	&\frac{\frac{\frac\testB\testB}\testB}\testB
\end{align*}

\end{document}

[evencoil]

that is excellent, thank you. This \mathchoice command is going to help me out in a lot of other regards as well. Many thanks!