Defined in header <locale>
template< class CharT >
bool islower( CharT ch, const locale& loc );

Checks if the given character is classified as a lowercase alphabetic character by the given locale's std::ctype facet.


ch - character
loc - locale

Return value

Returns true if the character is classified as lowercase, false otherwise.

Possible implementation

template< class CharT >
bool islower( CharT ch, const std::locale& loc ) {
    return std::use_facet<std::ctype<CharT>>(loc).is(std::ctype_base::lower, ch);


Demonstrates the use of islower() with different locales (OS-specific).

#include <iostream>
#include <locale>
int main()
    const wchar_t c = L'\u03c0'; // greek small letter pi
    std::locale loc1("C");
    std::cout << "islower('π', C locale) returned "
               << std::boolalpha << std::islower(c, loc1) << '\n';
    std::locale loc2("en_US.UTF8");
    std::cout << "islower('π', Unicode locale) returned "
              << std::boolalpha << std::islower(c, loc2) << '\n';

Possible output:

islower('π', C locale) returned false
islower('π', Unicode locale) returned true

See also

checks if a character is lowercase
checks if a wide character is lowercase

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