Re: math alphabets, WAS: Proprietary Card Decks

From: Doug Ewell (
Date: Thu Apr 14 2011 - 09:13:56 CDT

  • Next message: Asmus Freytag: "Re: math alphabets, WAS: Proprietary Card Decks"

    Hans Aberg <haberg dash 1 at telia dot com> wrote:

    >>> Unicode does not have characters for say superscripts and
    >>> subscripts, which are essential to math. My guess it would be too
    >>> complicated to require it for current text-only renderers, but in
    >>> the future that might change.
    >> No, because in math, superscript is not a character attribute but a
    >> formatting style that is applied to any term or formula and that can
    >> be fully (and infinitely) nested.
    >> That abstraction is better handled in markup than in plain text.
    >> (Unlike the mathalphanumerics, such markup is still independent of
    >> the font).
    > That is so in rendering programs like TeX, because one does not enter
    > the math so that it can be parsed semantically. One enters
    > superscripts how they should be rendered and not by the logical
    > structure of the formula.
    > That is different if one has say a theorem prover. Then one can enter
    > a formula, let the program parse it into an AST, and from that infer
    > how it should be rendered, for example, where to put parenthesizes.

    I don't follow this. Asmus' point is that superscript can be applied,
    not only to any arbitrary character that can be used in a math
    expression, but also at any arbitrary level of nesting. After Unicode
    has finished adding superscript versions of every imaginable math
    character, including all of the math alphanumerics, it would then have
    to add second-level, third-level, etc. versions of every character, so
    that one could enter "a to the b to the c to the (d times square root of
    2)" in plain text. And don't forget subscripts of superscripts, and
    vice versa.

    A counterargument that this is going too far, that Unicode wouldn't need
    to encode arbitrary levels of superscript/subscript nesting but only
    one, is basically an agreement with Asmus that this problem is best
    solved by (semantic) markup.

    Doug Ewell | Thornton, Colorado, USA | RFC 5645, 4645, UTN #14 | | @DougEwell ­

    This archive was generated by hypermail 2.1.5 : Thu Apr 14 2011 - 09:20:05 CDT