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I am writing some functions to manipulate strings. A typical way to produce a character with a given character code is the \lowercase primitive. The following code produces a character with code 234, and displays it to the terminal.

\lccode`*=234
\lowercase{\message{*}}

If I replace 234 by 345 above, then pdfTeX raises an error: Invalid code (345), should be in the range 0..255. On the other hand, LuaTeX and XeTeX are happy up to 1114111, as expected from a Unicode-compliant engine.

Now, I want my macros to be as robust as possible. Is it always true that the maximum lccode is 255 in pdfTeX and 1114111 in LuaTeX and XeTeX? Or can a user prevent in any way the engine from using the full range, hence confusing my macros?

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    AFAIK, XeTeX and LuaTeX can use a different input encoding. But the two engines both always use Unicode internally.
    – Leo Liu
    Commented Nov 25, 2011 at 22:21
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    I'd say yes. Why shouldn't it be true? As Leo Liu remarks, there's \XeTeXinputencoding that does a conversion of the input into Unicode, but that's all; when a character enters XeTeX it's changed into its Unicode correspondent in a way similar to the ^^ and ^^^^ conventions: the mouth will act on the changed character and so \lowercase and \uppercase need the whole set.
    – egreg
    Commented Nov 25, 2011 at 22:35
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    @LeoLiu: that's also my thought, but could there be some command-line switch? (I'm thinking of the difference between pdftex and pdfetex, where the former disables some commands.)
    – Bruno Le Floch
    Commented Nov 25, 2011 at 23:19
  • I've no idea. You'd better ask the maintainers.
    – Leo Liu
    Commented Nov 26, 2011 at 7:22
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    The luatex manual says quite clearly that \char now accepts values between 0 and 1114111 and extends this statement to the other similar commands like \lccode. As far as I know this is true in xetex too. (But the etex extension can be disabled in both engines).
    – Ulrike Fischer
    Commented Nov 26, 2011 at 9:23

2 Answers 2

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The LuaTeX manual says quite clearly that \char now accepts values between 0 and 1114111 and extends this statement to the other similar commands like \lccode. As far as I know this is true in XeTeX too. And IMHO a command line to change this seems rather senseless.

But the eTeX extension can be disabled in both engines. Or more precisely: XeTeX has a command line option to enable the eTeX extension (which is used by default by all TeX Systems) and LuaTeX has a similar feature. So it is possible to build a format manually which doesn't use them. But this affects only the eTeX relevant commands.

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I had a lot of 'old' documents and I didn't want to change to utf-8.

I used the following code in my preamble to use the 'old' encoding:

\ifxetex
  \XeTeXinputencoding "cp1252" % actual document
  \XeTeXdefaultencoding "cp1252" % sequent documents (\input)
\fi    
\usepackage[latin1]{luainputenc}

I don't know if this will make problems with your code - but you can try it.

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    -1. I'm sure that Bruno knows that input encodings can be changed. But the question is about internal encodings. \XeTeXinputencoding does nothing with \lccode. Moreover, \XeTeXdefaultencoding "cp1252" is dangerous because LaTeX itself writes some auxiliary files and they're always UTF-8 files. BTW, UTF-8 is compatible with Latin-1 encoding, but Latin-1 and cp1252 are different, cp1252 is superset of latin-1.
    – Leo Liu
    Commented Nov 26, 2011 at 7:25
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    @LeoLiu: you were maybe a little bit harsh. I indeed knew/expected that XeTeX would be able to somehow change input encodings, and here knut gives me a precise example of use. So the answer is off topic, but still useful for me.
    – Bruno Le Floch
    Commented Nov 26, 2011 at 8:46
  • @Leo - A quibble, I'm not sure what you wrote is what you meant to write: latin-1 is not compatible with utf-8. For example, the hex-encoded two-byte string C3 B6 corresponds to the character ö in utf-8 and the two characters ö in latin-1.
    – Charles Stewart
    Commented Nov 28, 2011 at 20:42
  • @Charles: I was wrong. ASCII is compatible with UTF-8. Say, UTF-8 is superset of ASCII.
    – Leo Liu
    Commented Nov 29, 2011 at 1:48

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