**From:** Kenneth Whistler (*kenw@sybase.com*)

**Date:** Tue Jul 27 2010 - 17:02:48 CDT

**Previous message:**Christoph Päper: "Re: Pashto yeh characters"**Maybe in reply to:**karl williamson: "Why does EULER CONSTANT not have math property and PLANCK CONSTANT does?"**Next in thread:**Asmus Freytag: "Re: Why does EULER CONSTANT not have math property and PLANCK CONSTANT does?"**Reply:**Asmus Freytag: "Re: Why does EULER CONSTANT not have math property and PLANCK CONSTANT does?"**Messages sorted by:**[ date ] [ thread ] [ subject ] [ author ] [ attachment ]**Mail actions:**[ respond to this message ] [ mail a new topic ]

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:

http://www.unicode.org/Public/math/revision-11/MathClassEx-11.txt

The contents of that file is not limited just to characters

with the value Math=True.

--Ken

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