E.4 R3 Pattern_White_Space and Pattern_Syntax characters[uaxid.pattern]
1 <https://eel.is/c++draft/uaxid.pattern#1>
#
<http://github.com/Eelis/draft/tree/6ed6196fdb12c126345be0d72caa6904ac5103b4/source/uax31.tex#L87>
UAX #31 describes how languages that use or interpret patterns of
characters, such as regular expressions or number formats, may describe
that syntax with Unicode properties.
<https://eel.is/c++draft/uaxid.pattern#1.sentence-1>
2 <https://eel.is/c++draft/uaxid.pattern#2>
#
<http://github.com/Eelis/draft/tree/6ed6196fdb12c126345be0d72caa6904ac5103b4/source/uax31.tex#L92>
C++ does not do this as part of the language, deferring to library
components for such usage of patterns.
<https://eel.is/c++draft/uaxid.pattern#2.sentence-1>

This requirement does not apply to C++.
<https://eel.is/c++draft/uaxid.pattern#2.sentence-2>

*1 <https://eel.is/c++draft/uaxid.pattern#1> *UAX#31 describes how formal
languages such as computer languages should describe and implement their
use of whitespace and syntactically significant characters during the
processes of lexing and parsing. C++ does not claim conformance with this
requirement.