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std:: islower (std::locale)

From cppreference.net
C++
Text processing library
Localization library
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.

Contents

Parameters

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);
}

Example

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

Run this code 
#include <iostream>
#include <locale>
int main()
{
    const wchar_t c = L'\u03c0'; // GREEK SMALL LETTER PI
    std::locale loc1("C");
    std::cout << std::boolalpha
              << "islower('π', C locale) returned "
              << std::islower(c, loc1) << '\n'
              << "isupper('π', C locale) returned "
              << std::isupper(c, loc1) << '\n';
    std::locale loc2("en_US.UTF8");
    std::cout << "islower('π', Unicode locale) returned "
              << std::islower(c, loc2) << '\n'
              << "isupper('π', Unicode locale) returned "
              << std::isupper(c, loc2) << '\n';
}

Possible output: 

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

See also

checks if a character is lowercase
(function)
checks if a wide character is lowercase
(function)