public static member function
<string>
static bool eq (const char_type& c, const char_type& d);
static constexpr bool eq (char_type c, char_type d) noexcept;
Compare characters for equality
Returns whether characters c and d are considered equal.
In the standard specializations of
char_traits, this function behaves as the built-in
operator==, but custom
character traits classes may provide an alternative behavior.
In the standard specializations of
char_traits, this function behaves as the built-in
operator== for type
unsigned char, but custom
character traits classes may provide an alternative behavior.
Parameters
- c, d
- Character values.
Member type char_type is the character type (i.e., the class template parameter in char_traits).
Return Value
true if c is considered equal to d.
Example
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// char_traits::eq
#include <iostream> // std::cout
#include <string> // std::basic_string, std::char_traits
#include <cctype> // std::tolower
#include <cstddef> // std::size_t
// traits with case-insensitive eq:
struct custom_traits: std::char_traits<char> {
static bool eq (char c, char d) { return std::tolower(c)==std::tolower(d); }
// some (non-conforming) implementations of basic_string::find call this instead of eq:
static const char* find (const char* s, std::size_t n, char c)
{ while( n-- && (!eq(*s,c)) ) ++s; return s; }
};
int main ()
{
std::basic_string<char,custom_traits> str ("Test");
std::cout << "T found at position " << str.find('t') << '\n';
return 0;
}
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Output:
Exception safety
No-throw guarantee: this member function never throws exceptions in any of the standard specializations.