Re: Some questions about fractions

From: Eric Muller (emuller@adobe.com)
Date: Tue Sep 30 2003 - 08:57:17 EDT

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    Jill Ramonsky wrote:

    > I'm wondering, exactly how equivalent are the following sequences:
    >
    > U+00BC (vulgar fraction one quarter)
    > U+215F U+0034 (fraction numerator one; digit four)
    > U+0031 U+2044 U+0034 (digit one; fraction slash; digit four)
    >
    > In particular, should they be rendered with the same glyph?

    I would rather phrase the question as ""if all characters involved are
    supported by a given layout system, should those three sequences produce
    the same visible result?" The first change is to account for an
    implementation not supporting, e.g., U+215F. The second change is to
    allow different glyph organizations, as long as they produce the same ink.

    That being said, I think the answer is yes, assuming non digits around
    the last one.

    > Is it possible to compose a single glyph for (say) twenty two over
    > seven, using the fraction slash?

    Sure. It is ok to have a single glyph for arbitrarily large fragments of
    text, fractions or not. If a glyph displaying "whole word" is available
    and appropriate for the circumstances, a rendering engine could use it.

    > If I were to write "one quarter" as U+0031 U+2044 U+0034, how should I
    > then write "one and a quarter"? Is there a "fraction space" which I
    > should use to separate the "1" from the "1/4"?

    Unicode 4.0 Section 6.2 p 159 has the answer:

        If the fraction is to be separated from a previous number, then a
        space can be used, choosing the appropriate width (normal, thin,
        zero width, and so on). For example 1 + THIN SPACE + 3 + FRACTION
        SLASH + 4 is displayed as 1.

    Eric.



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