Re: Why does EULER CONSTANT not have math property and PLANCK CONSTANT does?

From: Kenneth Whistler (
Date: Tue Jul 27 2010 - 17:02:48 CDT

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    Karl Williamson asked:

    > Subject: Why does EULER CONSTANT not have math property and PLANCK CONSTANT does?

    > They are U+2107 and U+210E respectively.

    Because U+210E PLANCK CONSTANT is, to quote the standard,
    "simply a mathematical italic h". It serves as the filler for
    the gap in the run of mathematical italic letters at U+1D455.

    All of the mathematical alphanumeric symbols are given
    the Other_Math property, and so also the derived Math property.
    And for consistency, any of the mathematical alphanumeric
    symbols omitted from the Mathematical Alphanumeric Symbols
    block, because the corresponding font-styled variant had
    already been encoded in the Letterlike Symbols block, are
    also given the Other_Math property.

    Other letterlike symbols in that block are not given the
    Other_Math property, even if they may be used in mathematical
    expressions. (Note that regular Greek letters are also not
    given the Other_Math property, even though they obviously also
    occur in mathematical expressions.)

    The Math property can be thought of as a hint that a particular
    symbol is specialized for mathematical usage; it isn't a
    property that any character that ever occurs in a mathematical
    expression needs to have. Nor is every character with
    the Math property only used in mathematical contexts.
    > Chapter 4 of TUS seems to
    > indicate that neither should, since they both are operands, and it says
    > this property applies to mathematical operators.

    Actually, Chapter 4 no longer says anything about the Math
    property. It is discussed in Section 15.4, Mathematical Symbols.

    That text still says:

    "The mathematical (math) property is an informative property of
    characters that are used as operators in mathematical formulas."

    Technically it doesn't say that it is a property *only* of such
    operators -- and obviously it isn't when you examine the actual
    list, since nobody considers the long list of mathematical
    alphanumeric symbols to be operators. So it might be nice
    if someone would propose an update to that text to better
    describe the actual set and so as not to give the misleading
    impression that it applies *only* to operators.

    Incidentally, much more detailed information about the classification
    of Unicode characters for math is available in the data file
    associated with UTR #25:

    The contents of that file is not limited just to characters
    with the value Math=True.


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