Constant lexical_util::format::CXX17_LITERAL

pub const CXX17_LITERAL: u128 = NumberFormatBuilder::new()
    .digit_separator(num::NonZeroU8::new(b'\''))
    .case_sensitive_special(true)
    .internal_digit_separator(true)
    .build(); // 0x0000_0a00_0000_0027_0000_0007_0000_080cu128

Number format for a C++17 literal floating-point number.