:relfileprefix: ../../../../
[#7959759509D8F8470BBB3DED31B97D5FC0389D01]

= Friend operator-

pass:v,q[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_]>`

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

== Description

pass:v,q[This function returns a new character] pass:v,q[set which is formed from all of the]
pass:v,q[characters in `cs0` which are not in `cs`.]

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

=== Complexity
pass:v,q[Constant.]