NAME¶

std::wmemcmp - std::wmemcmp

Synopsis¶

Defined in header <cwchar>
int wmemcmp( const wchar_t* lhs, const wchar_t* rhs, std::size_t count );

Compares the first count wide characters of the wide character arrays pointed to by
lhs and rhs. The comparison is done lexicographically.

The sign of the result is the sign of the difference between the values of the first
pair of wide characters that differ in the arrays being compared.

If count is zero, the function does nothing.

Parameters¶

lhs, rhs - pointers to the wide character arrays to compare
count - number of wide characters to examine

Return value¶

Negative value if the value of the first differing wide character in lhs is less
than the value of the corresponding wide character in rhs: lhs precedes rhs in
lexicographical order.

0 if all count wide characters of lhs and rhs are equal.

Positive value if the value of the first differing wide character in lhs is greater
than the value of the corresponding wide character in rhs: rhs precedes lhs in
lexicographical order.

Notes¶

This function is not locale-sensitive and pays no attention to the values of the
wchar_t objects it examines: nulls as well as invalid wide characters are compared
too.

Example¶

// Run this code

#include <clocale>
#include <cwchar>
#include <iostream>
#include <locale>
#include <string>

void demo(const wchar_t* lhs, const wchar_t* rhs, std::size_t sz)
{
std::wcout << std::wstring(lhs, sz);
int rc = std::wmemcmp(lhs, rhs, sz);
if (rc == 0)
std::wcout << " compares equal to ";
else if (rc < 0)
std::wcout << " precedes ";
else if (rc > 0)
std::wcout << " follows ";
std::wcout << std::wstring(rhs, sz) << " in lexicographical order\n";
}

int main()
{
std::setlocale(LC_ALL, "en_US.utf8");
std::wcout.imbue(std::locale("en_US.utf8"));

wchar_t a1[] = {L'α',L'β',L'γ'};
constexpr std::size_t sz = sizeof a1 / sizeof *a1;
wchar_t a2[sz] = {L'α',L'β',L'δ'};

demo(a1, a2, sz);
demo(a2, a1, sz);
demo(a1, a1, sz);
}

Possible output:¶

αβγ precedes αβδ in lexicographical order
αβδ follows αβγ in lexicographical order
αβγ compares equal to αβγ in lexicographical order

See also¶

wcscmp compares two wide strings
(function)
memcmp compares two buffers
(function)
wcsncmp compares a certain amount of characters from two wide strings
(function)
C documentation for
wmemcmp