Standard C++ Library Reference ISO/IEC (VERSION3)

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<wctype.h>
[Added with Amendment 1]
iswalnum · iswalpha · iswcntrl · iswdigit · iswgraph · iswlower
· iswprint · iswpunct · iswspace · iswupper · iswxdigit ·
towlower · towctrans · towupper · wctrans · wctype
Include the standard header <wctype.h> to declare several functions that are useful for
classifying and mapping codes from the target wide-character set.
Every function that has a parameter of type wint_t can accept the value of the macro WEOF or
any valid wide-character code (of type wchar_t). Thus, the argument can be the value
returned by any of the functions: btowc, fgetwc, fputwc, getwc, getwchar, putwc,
putwchar, towctrans, towlower, towupper, or ungetwc. You must not call these
functions with other wide-character argument values.
The wide-character classification functions are strongly related to the (byte) character
classification functions. Each function isXXX has a corresponding wide-character classification
function iswXXX. Moreover, the wide-character classification functions are interrelated much
the same way as their corresponding byte functions, with two added provisos:
The function iswprint, unlike isprint, can return a nonzero value for additional
space characters besides the wide-character equivalent of space (L' '). Any such
additional characters return a nonzero value for iswspace and return zero for
iswgraph or iswpunct.
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The characters in each wide-character class are a superset of the characters in the
corresponding byte class. If the call isXXX(c) returns a nonzero value, then the
corresponding call iswXXX(btowc(c)) also returns a nonzero value.
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An implementation can define additional characters that return nonzero for some of these
functions. Any character set can contain additional characters that return nonzero for:
iswcntrl (provided the characters cause iswprint to return zero)●
iswpunct (provided the characters cause iswalnum to return zero)●
Moreover, a locale other than the "C" locale can define additional characters for:
iswalpha, iswupper, and iswlower (provided the characters cause iswcntrl,
iswdigit, iswpunct, and iswspace to return zero)
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iswspace (provided the characters cause iswpunct to return zero)●