E.4 R3 Pattern_White_Space and Pattern_Syntax characters[uaxid.pattern]

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.
C++ does not do this as part of the language, deferring to library components for such usage of patterns.
 
This requirement does not apply to C++.

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.