Re: Roman Numerals (was Re: Improper grounds for rejection of proposal N2677)

From: Jukka K. Korpela (
Date: Wed Nov 02 2005 - 00:39:24 CST

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    On Tue, 1 Nov 2005, Philippe Verdy wrote:

    > Tip: for HTML you can use:
    > 2<sup><span style="display:none;">^</span>2</sup>

    That's an interesting idea, but there are three reasons why it does not
    - we cannot expect that people generally recognize "^" as indicating
       exponentiation; it's basically computer programmin jargon
    - whether <sup> is implemented suitably by a browser does not
       depend on its CSS support, so on most browsers, when CSS is
       disabled or the author style sheet is not used, the user would
       see "^2" in superscript style
    - browsers that cannot generally implement <sup>, e.g. because they
       essentially render the document using plain text only ("character cell
       browsers") or they work in non-visual mode, may well use some
       special notations to indicate the presence of superscripting;
       e.g., Lynx renders your example as 2^^2 because it renders
       <sup>foo</sup> as ^foo (which is debatable, but surely useful
       at times).

    I think the morale is that expressing superscripting in _several_
    ways generally not a good idea, because the ways may interact

    Replacing <sup> with semantically empty markup and suitable CSS
    would give more consistent results:

    2<span class="aux">^</span><span class="sup">2</span>

    with e.g. .sup { vertical-align: super; font-size: 80%; }
    .aux { display: none; }

    It's not safe, though; anything that expects CSS settings to be coupled
    with each other is unsafe. Besides, it loses the semantics of <sup>
    and gives suboptimal rendering when CSS is turned off on a graphic

    So I would say that if you use markup for superscripts, then that should
    be it. The markup might not be honored in all contexts, but attempts
    to prepare for such situations will be both awkward and unreliable.
    If you cannot rely on markup to a sufficient degree, then the options
    are to use superscript characters (in the fairly limited situations
    where they can be used and can be expected to work) and to express
    yourself in other ways, e.g. using linearized plain text notations
    that you explain in text, whether that be 2^2, 2**2, pow(2,2), or
    something else. Incidentally, when exponentiation is to be expressed
    compactly in plain text, then I think UPWARDS ARROW U+2191 would
    be a better symbol than circumflex ^ (which was originally taken
    into use in exponential expressions since it can be imagined to be
    a simulation of an upwards arrow).

    Jukka "Yucca" Korpela,

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