macrosmath-mode
I'd like to write e^x in LaTeX math mode where the e is written upright, rather than slanted, to indicate that it is not a variable. Kopka and Daly (4ed) pg. 285 do this with \me^x. When I try this I get the "undefined control sequence" error.
Q: Is \me a deprecated command?
Q: How can I do now what \me used to do?
I don't think you really wants this. However, here it is:
\documentclass{article}
\usepackage{amsmath}
\newcommand{\xnorm}[1]{%
\mathchoice{\Bigl\|#1\Bigr\|}{\lVert#1\rVert}{\lVert#1\rVert}{\lVert#1\rVert}%
}
\begin{document}
A norm in text mode is $\xnorm{v}$, while in display math it is
\[
\xnorm{v}=\sum_{i=1}^n\lvert v_i\rvert
\]
\end{document}
The result is really ugly (and wrong):
If you change \Bigl and \Bigr with \bigl and \bigr you get a more acceptable result, but I can't see the point of increasing the fences' size.
I wouldn't use \limits in this case since it'll end up placing the lower and upper limits of the sequence below and above the right-hand curly brace -- probably not what you intended.
If you write \{h_{n}\}_{0}^{\infty}$ (see the middle example below, labelled "not awful"), the upper and lower limits may look like they're too close to each other, especially in text-style math mode. One way to fix this is to encase the closing curly brace, \}, in a pair of braces to change its status from "math-close" to "math-ordinary"; doing so will loosen the spacing quite a bit.
It may be best, though, to define a custom macro called, say, \seqwlimits to standardize the task at hand and to assure adequate vertical separation of the upper and lower limits.
\documentclass{article}
\newcommand\seqwlimits[3]{\{#1\}_{\mathstrut#2}^{\mathstrut#3}}
\begin{document}
\begin{tabular}{ll}
huh?? & ${\{h_{n}\}}\limits_{0}^{\infty}$\\[2ex]
awful & $\{h_{n}\}\limits_{0}^{\infty}$\\[2ex]
not awful& $\{h_{n}\}_{0}^{\infty}$\\[2ex]
better & $\{h_{n}{\}}_{0}^{\infty}$\\[2ex] % note the extra { and }
best & $\seqwlimits{h_n}{0}{\infty}$\\
\end{tabular}
\end{document}
Best Answer
You have to define yourself that command in your document preamble
Some comments
It's not necessary to declare this symbol as an ordinary symbol because by rule all math characters that are subject to alphabet changes are ordinary.
The construction
\mathrm{e}is essentially equivalent tobecause the Roman math alphabet corresponds to the math group 0. Each math alphabet (
\mathrm,\mathnormal,\mathbfand so on) corresponds to the choice of one among 16 math groups;\mathrmis 0,\mathnormalis 1, the others are from 4 onwards.Each character has a
\mathcodewhich, foreis"7165which meansThus calling
\mathrm{e}is like asking for a math code"0065(numbers preceded by"are hexadecimal): the first 0 means "ordinary symbol", the second one is the math group. With\mathbf{e}we would ask for"0465, according to the normal LaTeX setup.Details about math codes are in the TeXbook or in TeX by Topic. Note that LaTeX calls
\mathgroupthe primitive\fam.