:relfileprefix: ../../../../
[#boost-urls-grammar-lut_chars-08friend-07]

= xref:boost.adoc[pass:[boost]]::xref:boost/urls.adoc[pass:[urls]]::xref:boost/urls/grammar.adoc[pass:[grammar]]::operator-


Return a new character set by subtracting


== Synopsis

Declared in header `<https://www.github.com/boostorg/url/blob/develop/include/boost/url/grammar/lut_chars.hpp#L336[boost/url/grammar/lut_chars.hpp,window=blank_]>`

[source,cpp,subs="verbatim,macros,-callouts"]
----
friend
constexpr
xref:boost/urls/grammar/lut_chars.adoc[lut_chars]
operator-(
    xref:boost/urls/grammar/lut_chars.adoc[lut_chars] const& cs0,
    xref:boost/urls/grammar/lut_chars.adoc[lut_chars] const& cs1) noexcept;
----

== Description


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

=== Example

This statement declares a character set
containing all the lowercase letters
which are not vowels:
[,cpp]
----
constexpr lut_chars consonants = lut_chars("abcdefghijklmnopqrstuvwxyz") - "aeiou";
----

=== Complexity

Constant.