Is there a way to use newcommand or some other nice technique to transform any occurence of
"bla"
in math mode into
\text{bla}
The reason I ask is because it is easy, and doesn't interrupt the flow of reading the (La)TeX code as much.
I would like to keep Xe(La)TeX's nice quote behavior (ie it can use the regular "" instead of backticks to quote some text outside math mode).
I don't think that marking code this way adds to its readability. Nevertheless, you can change the behavior of " in math mode with the following TeX magic:
\documentclass{article}
\usepackage{amsmath}
\begingroup\lccode`~=`"
\lowercase{\endgroup\def~}#1"{\text{#1}}
\mathcode`"="8000
\begin{document}
"Abc" $f_"abc"$
\end{document}
However, keep in mind that " is not the “right” way to type a double quote, and it's preferable to use the combinations `` and ''.
If the quotes your text editor inserts are “ and ”, then the following should work:
\begingroup\lccode`~=`“
\lowercase{\endgroup\def~}#1”{\text{#1}}
\mathcode`“="8000
But definitely not when using pdflatex and UTF-8 encoding. XeLaTeX and LuaLaTeX are OK. Again, I don't recommend such a type of markup, which is prone to errors and less readable than an explicit \text{...} markup.
Let's see how it works; the trick
\begingroup\lccode`~=`“
\lowercase{\endgroup\def~}#1”{\text{#1}}
is very common (it's in the TeXbook) in order to give a meaning to the active version of a character (in this case “) as \lowercase does its job and puts the converted token list back in the input stream, so that TeX will see the lowercase version of ~ (still active as is ~ in the default setting). Thus TeX will swallow
\def“#1”{\text{#1}}
The macro “ is defined to look for the following ” and consider anything in between as its argument, which is passed to \text.
With \mathcode`“="8000 we are telling (Xe)TeX that “ in math mode must be converted to its active version. In text mode the nature of “ is not changed.
Why does the first version, with ", work? Because " is not active, its category code is still 12 and the definition tells TeX to look for the next category 12 " that follow (it's converted to a mathcode only if it need to be, that is, if TeX is looking for mathcodes, which it doesn't when collecting the parameter text of a called macro).
Why doesn't the version with “ work with pdflatex? Because this is not a seven bit character, so pdftex sees it as two characters (it's even wrong to say \lccode`~=`“, in pdftex, as a stray character will remain). With XeTeX or LuaTeX, instead, multibyte characters are converted to a single entity before the engine starts the tokenization process.
“” (which ensures the "right" quoting in the final output). I cannot seem to determine the "begin" and "endquote" in your TeX magic. Is it possible or is you method only suited for the same opening as closing character?
– rubenvb
Dec 12 '11 at 13:24
" in the \def not also be active? Could you explain the \mathcode"="8000` line a little?
– Martin Scharrer
Dec 12 '11 at 15:07
" doesn't have to be active; there is no such restriction on non-parameter tokens in parameter texts. A mathcode of 8000h means math-active: in math mode, the character is treated as if it were active, and TeX uses its meaning.
– Philipp
Dec 12 '11 at 23:04
" is found, its mathcode is relevant, so it is changed into its active counterpart, which is then expanded: its argument is delimited by a category 12 ".
– egreg
Dec 12 '11 at 23:12
\mathcode thing, which is kind of new to me.
– Martin Scharrer
Dec 13 '11 at 09:44
\catcode`"=13, when the definition of the active dblquote is performed: you see that the final dblquote of the parameter text is outside the \lowercase.
– egreg
Dec 13 '11 at 11:43
\mathcode so far, that was the reason I asked the question.
– Martin Scharrer
Dec 13 '11 at 17:20
You can do this by making " active (like e.g. ~ is) and define it as a macro which looks for another " as end-marker. You need to use the TeX \def primitive instead of LaTeX \newcommand macro:
\documentclass{article}
\usepackage{amsmath}
\catcode`\"=\active
\def"#1"{\text{#1}}
\begin{document}
"bla"
\text{bla}
$ a_{"bla"} = b_{\text{bla}} $
\end{document}
If you want to allow whole paragraphs add a \long before \def.
You have to be careful with packages which also redefine " like babel with some languages. You should have the above code after loading such packages.
\text{}commands to improve general readability of the tex code. – rubenvb Dec 12 '11 at 13:01