Friend operator-

Return a new character set by subtracting

Synopsis

Declared in header </boost/url/grammar/lut_chars.hpp#L328[boost/url/grammar/lut_chars.hpp,window=blank_]>

friend
constexpr
lut_chars
operator-(
    const lut_chars& cs0,
    const lut_chars& cs1) noexcept;

This function returns a new character set which is formed from all of the characters in cs0 which are not in cs.

This statement declares a character set containing all the lowercase letters which are not vowels:

constexpr lut_chars consonants = lut_chars("abcdefghijklmnopqrstuvwxyz") - "aeiou";

Constant.