std::ctype<char>::scan_is

 

C++

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Concepts library (C++20)

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Technical Specifications

 

Localizations library

Locales and facets
locale
use_facet	has_facet
Character classification
isspace isblank (C++11) iscntrl isupper islower isalpha	isdigit ispunct isxdigit isalnum isprint isgraph
Conversions
toupper tolower	wstring_convert (C++11) wbuffer_convert (C++11)
Facet category base classes
ctype_base codecvt_base messages_base	time_base money_base
Facet categories
ctype ctype<char> codecvt collate messages time_get time_put	num_get num_put numpunct money_get money_put moneypunct
Locale-specific facets
ctype_byname codecvt_byname messages_byname collate_byname	time_get_byname time_put_byname numpunct_byname moneypunct_byname
Code conversion facets
codecvt_utf8 (C++11) codecvt_utf16 (C++11)	codecvt_utf8_utf16 (C++11) codecvt_mode (C++11)
C locale
setlocale localeconv lconv	LC_ALLLC_COLLATELC_CTYPELC_MONETARYLC_NUMERICLC_TIME

 

std::ctype

Member functions

ctype::ctype

ctype::~ctype

ctype::isctype::do_is

ctype::scan_isctype::do_scan_is

ctype::scan_notctype::do_scan_not

ctype::toupperctype::do_toupper

ctype::tolowerctype::do_tolower

ctype::widenctype::do_widen

ctype::narrowctype::do_narrow

Member functions of ctype<char>

ctype<char>::ctype

ctype<char>::~ctype

ctype<char>::table

ctype<char>::classic_table

ctype<char>::is

ctype<char>::scan_is

ctype<char>::scan_not

 

Defined in header <locale>
const char* scan_is (mask m, const char* beg, const char* end) const;	(1)

Locates the first character in the character array [beg, end) that satisfies the classification mask m, that is, the first character c such that table()[(unsigned char) c] & m would return true.

If (unsigned char)c >= std::ctype<char>::table_size, then an implementation-defined value is substituted instead of table()[(unsigned char)c], possibly different for different values of c.

Parameters

m	-	mask to search for
beg	-	pointer to the first character in an array of characters to search
end	-	one past the end pointer for the array of characters to search

Return value

Pointer to the first character in [beg, end) that satisfies the mask, or end if no such character was found.

Notes

Unlike the primary template std::ctype, this specialization does not perform a virtual function call when classifying characters. To customize the behavior, a derived class may provide a non-default classification table to the base class constructor.

Example

Run this code

#include <locale>
#include <iostream>
#include <iterator>
 
int main()
{
    std::locale loc("");
    auto& f = std::use_facet<std::ctype<char>>(loc);
 
    // skip until the first letter
    char s1[] = "      \t\t\n  Test";
    const char* p1 = f.scan_is(std::ctype_base::alpha, std::begin(s1), std::end(s1));
    std::cout << "'" << p1 << "'\n";
 
    // skip until the first letter
    char s2[] = "123456789abcd";
    const char* p2 = f.scan_is(std::ctype_base::alpha, std::begin(s2), std::end(s2));
    std::cout << "'" << p2 << "'\n";
}

Output:

'Test'
'abcd'

See also

do_scan_is [virtual]	locates the first character in a sequence that conforms to given classification (virtual protected member function of std::ctype<CharT>)
scan_not	locates the first character in a sequence that fails given classification, using the classification table (public member function)