https://docs.rs/unicode-math-class/0.1.0/unicode_math_class/
enum math-class
https://docs.rs/unicode-math-class/0.1.0/unicode_math_class/enum.MathClass.html
normal
alphabetic
binary
closing
diacritic
fence
glyph-part
large
opening
punctuation
relation
space
unary
vary
special
revision: func
https://docs.rs/unicode-math-class/0.1.0/unicode_math_class/constant.REVISION.html
class: func
https://docs.rs/unicode-math-class/0.1.0/unicode_math_class/fn.class.html
c
: string
math-class
>