STD::CTYPE(3)

💖 std::ctype< _CharT > 💖

Library Functions Manual · section 3 — ok bestie, this is the big one, the primary class template ctype facet, and we are gonna get through it together 🫶

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🎀 NAME 🎀

std::ctype< _CharT > — the primary class template ctype facet. that's the whole vibe. it's the thing that knows what a letter is and what a digit is ✨

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✨ SYNOPSIS ✨

#include <locale>

Inherits std::__ctype_abstract_base< _CharT >.

Inherited by std::ctype_byname< _CharT >.

🦋 Public Types 🦋

• typedef const int * __to_type
• typedef _CharT char_type
• typedef __ctype_abstract_base< _CharT >::mask mask

🦋 Public Member Functions 🦋

• ctype (size_t __refs=0)
• const char_type * is (const char_type *__lo, const char_type *__hi, mask *__vec) const — hand you back a whole mask array, one entry per character.
• bool is (mask __m, char_type __c) const — the vibe check: is this character that kind of character?
• char narrow (char_type __c, char __dfault) const — squish a char_type down into a plain char.
• const char_type * narrow (const char_type *__lo, const char_type *__hi, char __dfault, char *__to) const — squish a whole array of them into a char array.
• const char_type * scan_is (mask __m, const char_type *__lo, const char_type *__hi) const — go find the first char_type that matches a mask.
• const char_type * scan_not (mask __m, const char_type *__lo, const char_type *__hi) const — go find the first char_type that doesn't match a mask.
• const char_type * tolower (char_type *__lo, const char_type *__hi) const — lowercase the whole array, glow-down ✨
• char_type tolower (char_type __c) const — lowercase just one.
• const char_type * toupper (char_type *__lo, const char_type *__hi) const — uppercase the whole array, RISE UP 👑
• char_type toupper (char_type __c) const — uppercase just one.
• char_type widen (char __c) const — stretch a plain char out into a char_type.
• const char * widen (const char *__lo, const char *__hi, char_type *__to) const — stretch a whole array out into char_type.

🦋 Static Public Attributes 🦋

• static const mask alnum
• static const mask alpha
• static const mask blank
• static const mask cntrl
• static const mask digit
• static const mask graph
• static locale::id id — the facet id for ctype<char_type>. it's giving identity, it's giving main character 🎀
• static const mask lower
• static const mask print
• static const mask punct
• static const mask space
• static const mask upper
• static const mask xdigit

🦋 Protected Member Functions 🦋

• virtual const char_type * do_is (const char_type *__lo, const char_type *__hi, mask *__vec) const — return a mask array.
• virtual bool do_is (mask __m, char_type __c) const — test char_type classification.
• virtual char do_narrow (char_type, char __dfault) const — narrow char_type to char.
• virtual const char_type * do_narrow (const char_type *__lo, const char_type *__hi, char __dfault, char *__to) const — narrow a char_type array to char.
• virtual const char_type * do_scan_is (mask __m, const char_type *__lo, const char_type *__hi) const — find a char_type matching a mask.
• virtual const char_type * do_scan_not (mask __m, const char_type *__lo, const char_type *__hi) const — find a char_type not matching a mask.
• virtual const char_type * do_tolower (char_type *__lo, const char_type *__hi) const — convert array to lowercase.
• virtual char_type do_tolower (char_type __c) const — convert to lowercase.
• virtual const char_type * do_toupper (char_type *__lo, const char_type *__hi) const — convert array to uppercase.
• virtual char_type do_toupper (char_type __c) const — convert to uppercase.
• virtual char_type do_widen (char __c) const — widen char.
• virtual const char * do_widen (const char *__lo, const char *__hi, char_type *__dest) const — widen a char array.

🦋 Static Protected Member Functions 🦋

• static __c_locale _S_clone_c_locale (__c_locale &__cloc) throw ()
• static void _S_create_c_locale (__c_locale &__cloc, const char *__s, __c_locale __old=0)
• static void _S_destroy_c_locale (__c_locale &__cloc)
• static __c_locale _S_get_c_locale ()
• static const char * _S_get_c_name () throw ()
• static __c_locale _S_lc_ctype_c_locale (__c_locale __cloc, const char *__s)

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🌸 Detailed Description 🌸

template<typename _CharT>
    class std::ctype< _CharT >"Primary class template ctype facet.

ok so listen 👂 this template class defines the classification and conversion functions for character sets. it wraps cctype functionality. Ctype gets used by streams for so many I/O operations, like it's booked and busy.

This template provides the protected virtual functions the developer will have to replace in a derived class or specialization to make a working facet. The public functions that access them are defined in __ctype_abstract_base, to allow for implementation flexibility. See ctype<wchar_t> for an example. The functions are documented in __ctype_abstract_base.

Note: implementations are provided for all the protected virtual functions, but will likely not be useful. 😭 (not the default impls being mid, but here we are)

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💅 Member Function Documentation 💅

template<typename _CharT> virtual const char_type * std::ctype< _CharT >::do_is (const char_type * __lo, const char_type * __hi, mask * __vec) const [protected], [virtual]

Return a mask array. This function finds the mask for each char_type in the range [lo,hi) and successively writes it to vec. vec must have as many elements as the input. 🔥

do_is() is a hook for a derived facet to change the behavior of classifying. do_is() must always return the same result for the same input. (consistency bestie, we stan ✨)

Parameters

• __lo — Pointer to start of range.
• __hi — Pointer to end of range.
• __vec — Pointer to an array of mask storage.

Returns

__hi.

Implements std::__ctype_abstract_base< _CharT >.

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template<typename _CharT> virtual bool std::ctype< _CharT >::do_is (mask __m, char_type __c) const [protected], [virtual]

Test char_type classification. This function finds a mask M for c and compares it to mask m.

do_is() is a hook for a derived facet to change the behavior of classifying. do_is() must always return the same result for the same input.

Parameters

• __c — The char_type to find the mask of.
• __m — The mask to compare against.

Returns

(M & __m) != 0.

Implements std::__ctype_abstract_base< _CharT >.

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template<typename _CharT> virtual char std::ctype< _CharT >::do_narrow (char_type __c, char __dfault) const [protected], [virtual]

Narrow char_type to char. This virtual function converts the argument to char using the simplest reasonable transformation. If the conversion fails, dfault is returned instead.

do_narrow() is a hook for a derived facet to change the behavior of narrowing. do_narrow() must always return the same result for the same input.

Note: this is not what you want for codepage conversions. See codecvt for that. 🫠 don't do it, bestie, that's a different department.

Parameters

• __c — The char_type to convert.
• __dfault — char to return if conversion fails.

Returns

The converted char.

Implements std::__ctype_abstract_base< _CharT >.

Referenced by std::ctype< char >::narrow(), and std::ctype< char >::narrow().

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template<typename _CharT> virtual const char_type * std::ctype< _CharT >::do_narrow (const char_type * __lo, const char_type * __hi, char __dfault, char * __to) const [protected], [virtual]

Narrow char_type array to char. This virtual function converts each char_type in the range [__lo,__hi) to char using the simplest reasonable transformation and writes the results to the destination array. For any element in the input that cannot be converted, __dfault is used instead. 💖

do_narrow() is a hook for a derived facet to change the behavior of narrowing. do_narrow() must always return the same result for the same input.

Note: this is not what you want for codepage conversions. See codecvt for that.

Parameters

• __lo — Pointer to start of range.
• __hi — Pointer to end of range.
• __dfault — char to use if conversion fails.
• __to — Pointer to the destination array.

Returns

__hi.

Implements std::__ctype_abstract_base< _CharT >.

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template<typename _CharT> virtual const char_type * std::ctype< _CharT >::do_scan_is (mask __m, const char_type * __lo, const char_type * __hi) const [protected], [virtual]

Find char_type matching mask. This function searches for and returns the first char_type c in [__lo,__hi) for which is(__m,c) is true. 🔍

do_scan_is() is a hook for a derived facet to change the behavior of match searching. do_is() must always return the same result for the same input.

Parameters

• __m — The mask to compare against.
• __lo — Pointer to start of range.
• __hi — Pointer to end of range.

Returns

Pointer to a matching char_type if found, else __hi.

Implements std::__ctype_abstract_base< _CharT >.

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template<typename _CharT> virtual const char_type * std::ctype< _CharT >::do_scan_not (mask __m, const char_type * __lo, const char_type * __hi) const [protected], [virtual]

Find char_type not matching mask. This function searches for and returns a pointer to the first char_type c of [lo,hi) for which is(m,c) is false. 🚫

do_scan_is() is a hook for a derived facet to change the behavior of match searching. do_is() must always return the same result for the same input.

Parameters

• __m — The mask to compare against.
• __lo — Pointer to start of range.
• __hi — Pointer to end of range.

Returns

Pointer to a non-matching char_type if found, else __hi.

Implements std::__ctype_abstract_base< _CharT >.

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template<typename _CharT> virtual const char_type * std::ctype< _CharT >::do_tolower (char_type * __lo, const char_type * __hi) const [protected], [virtual]

Convert array to lowercase. This virtual function converts each char_type in the range [__lo,__hi) to lowercase if possible. Other elements remain untouched. 🍓

do_tolower() is a hook for a derived facet to change the behavior of lowercasing. do_tolower() must always return the same result for the same input.

Parameters

• __lo — Pointer to start of range.
• __hi — Pointer to end of range.

Returns

__hi.

Implements std::__ctype_abstract_base< _CharT >.

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template<typename _CharT> virtual char_type std::ctype< _CharT >::do_tolower (char_type __c) const [protected], [virtual]

Convert to lowercase. This virtual function converts the argument to lowercase if possible. If not possible (for example, '2'), returns the argument. bestie a '2' is a '2', we can't lowercase it and that's fine 🙈

do_tolower() is a hook for a derived facet to change the behavior of lowercasing. do_tolower() must always return the same result for the same input.

Parameters

• __c — The char_type to convert.

Returns

The lowercase char_type if convertible, else __c.

Implements std::__ctype_abstract_base< _CharT >.

Referenced by std::ctype< char >::tolower(), and std::ctype< char >::tolower().

do_toupper — array edition 💅

template<typename _CharT> virtual const char_type * std::ctype< _CharT >::do_toupper (char_type * __lo, const char_type * __hi) const

[protected], [virtual]

okay so this one converts every single char_type in the range [__lo,__hi) to uppercase if possible. Anything it can't convert just stays exactly as it was — no touchy. ✨

do_toupper() is a hook so a derived facet can change the behavior of uppercasing. And the rule? do_toupper() must always return the same result for the same input. no cap. 🔥

Parameters

• __lo — pointer to the start of the range.
• __hi — pointer to the end of the range.

Returns

__hi.

Implements std::__ctype_abstract_base< _CharT >.

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do_toupper — single char edition 🎀

template<typename _CharT> virtual char_type std::ctype< _CharT >::do_toupper (char_type __c) const

[protected], [virtual]

Converts the char_type argument to uppercase if possible. If it's not possible (think '2'), it just hands the argument right back to you, unchanged. 💖

Same deal as before: do_toupper() is a hook for a derived facet to change the behavior of uppercasing, and do_toupper() must always return the same result for the same input.

Parameters

• __c — the char_type to convert.

Returns

The uppercase char_type if convertible, else __c.

Implements std::__ctype_abstract_base< _CharT >.

Referenced by std::ctype< char >::toupper(), and std::ctype< char >::toupper().

bestie it literally says the same referencer twice in the source. we don't make the rules 💀

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do_widen — one char in 🦋

template<typename _CharT> virtual char_type std::ctype< _CharT >::do_widen (char __c) const

[protected], [virtual]

Widening time! This virtual function converts the char to char_type using the simplest reasonable transformation.

do_widen() is a hook for a derived facet to change the behavior of widening, and do_widen() must always return the same result for the same input.

Note: this is not what you want for codepage conversions. See codecvt for that. 🙈

Parameters

• __c — the char to convert.

Returns

The converted char_type.

Implements std::__ctype_abstract_base< _CharT >.

Referenced by std::ctype< char >::widen(), and std::ctype< char >::widen().

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do_widen — whole array 🌈

template<typename _CharT> virtual const char * std::ctype< _CharT >::do_widen (const char * __lo, const char * __hi, char_type * __to) const

[protected], [virtual]

Widen char array ✨ — this function converts each char in the input to char_type using the simplest reasonable transformation.

do_widen() is a hook for a derived facet to change the behavior of widening, and do_widen() must always return the same result for the same input.

Note: this is not what you want for codepage conversions. See codecvt for that. 🙈

Parameters

• __lo — pointer to start range.
• __hi — pointer to end of range.
• __to — pointer to the destination array.

Returns

__hi.

Implements std::__ctype_abstract_base< _CharT >.

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is — mask array version 👑

template<typename _CharT> const char_type * std::__ctype_abstract_base< _CharT >::is (const char_type * __lo, const char_type * __hi, mask * __vec) const

[inline], [inherited]

Return a mask array. This function finds the mask for each char_type in the range [lo,hi) and successively writes it to vec. Important: vec must have as many elements as the char array. It does all this by returning the value of ctype<char_type>::do_is().

Parameters

• __lo — pointer to start of range.
• __hi — pointer to end of range.
• __vec — pointer to an array of mask storage.

Returns

__hi.

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is — single char check 💜

template<typename _CharT> bool std::__ctype_abstract_base< _CharT >::is (mask __m, char_type __c) const

[inline], [inherited]

Test char_type classification, bestie. This function finds a mask M for __c and compares it to mask __m. It does so by returning the value of ctype<char_type>::do_is().

Parameters

• __c — the char_type to compare the mask of.
• __m — the mask to compare against.

Returns

(M & __m) != 0.

Referenced by std::time_get< _CharT, _InIter >::get().

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narrow — single char down to char 🌸

template<typename _CharT> char std::__ctype_abstract_base< _CharT >::narrow (char_type __c, char __dfault) const

[inline], [inherited]

Narrow char_type to char. This function converts the char_type to char using the simplest reasonable transformation. If the conversion fails, dfault is returned instead. It does so by returning ctype<char_type>::do_narrow(__c).

Note: this is not what you want for codepage conversions. See codecvt for that. 🙈

Parameters

• __c — the char_type to convert.
• __dfault — char to return if conversion fails.

Returns

The converted char.

Referenced by std::time_get< _CharT, _InIter >::do_get_year(), std::time_get< _CharT, _InIter >::get(), and std::time_put< _CharT, _OutIter >::put().

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narrow — whole array edition 🧚

template<typename _CharT> const char_type * std::__ctype_abstract_base< _CharT >::narrow (const char_type * __lo, const char_type * __hi, char __dfault, char * __to) const

[inline], [inherited]

Narrow array to char array. This function converts each char_type in the input to char using the simplest reasonable transformation and writes the results to the destination array. For any char_type in the input that cannot be converted, dfault is used instead. It does so by returning ctype<char_type>::do_narrow(__lo, __hi, __dfault, __to).

Note: this is not what you want for codepage conversions. See codecvt for that. 🙈

Parameters

• __lo — pointer to start of range.
• __hi — pointer to end of range.
• __dfault — char to use if conversion fails.
• __to — pointer to the destination array.

Returns

__hi.

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scan_is — find the first match 🔍

template<typename _CharT> const char_type * std::__ctype_abstract_base< _CharT >::scan_is (mask __m, const char_type * __lo, const char_type * __hi) const

[inline], [inherited]

Find char_type matching a mask. This function searches for and returns the first char_type c in [lo,hi) for which is(m,c) is true. It does so by returning ctype<char_type>::do_scan_is().

Parameters

• __m — the mask to compare against.
• __lo — pointer to start of range.
• __hi — pointer to end of range.

Returns

Pointer to matching char_type if found, else __hi.

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scan_not — find the first non-match 🙅

template<typename _CharT> const char_type * std::__ctype_abstract_base< _CharT >::scan_not (mask __m, const char_type * __lo, const char_type * __hi) const

[inline], [inherited]

Find char_type not matching a mask. This function searches for and returns the first char_type c in [lo,hi) for which is(m,c) is false. It does so by returning ctype<char_type>::do_scan_not().

Parameters

• __m — the mask to compare against.
• __lo — pointer to first char in range.
• __hi — pointer to end of range.

Returns

Pointer to non-matching char if found, else __hi.

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tolower — array edition 🍓

template<typename _CharT> const char_type * std::__ctype_abstract_base< _CharT >::tolower (char_type * __lo, const char_type * __hi) const

[inline], [inherited]

Convert array to lowercase. This function converts each char_type in the range [__lo,__hi) to lowercase if possible. Other elements remain untouched. It does so by returning ctype<char_type>:: do_tolower(__lo, __hi).

Parameters

• __lo — pointer to start of range.
• __hi — pointer to end of range.

Returns

__hi.

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tolower — single char 🌱

template<typename _CharT> char_type std::__ctype_abstract_base< _CharT >::tolower (char_type __c) const

[inline], [inherited]

Convert to lowercase. This function converts the argument to lowercase if possible. If not possible (for example, '2'), it returns the argument. It does so by returning ctype<char_type>::do_tolower(c).

Parameters

• __c — the char_type to convert.

Returns

The lowercase char_type if convertible, else __c.

Referenced by std::time_get< _CharT, _InIter >::get().

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toupper — array edition ⬆️

template<typename _CharT> const char_type * std::__ctype_abstract_base< _CharT >::toupper (char_type * __lo, const char_type * __hi) const

[inline], [inherited]

Convert array to uppercase. This function converts each char_type in the range [lo,hi) to uppercase if possible. Other elements remain untouched. It does so by returning ctype<char_type>:: do_toupper(lo, hi).

Parameters

• __lo — pointer to start of range.
• __hi — pointer to end of range.

Returns

__hi.

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toupper — single char 🆙

template<typename _CharT> char_type std::__ctype_abstract_base< _CharT >::toupper (char_type __c) const

[inline], [inherited]

Convert to uppercase. This function converts the argument to uppercase if possible. If not possible (for example, '2'), it returns the argument. It does so by returning ctype<char_type>::do_toupper().

Parameters

• __c — the char_type to convert.

Returns

The uppercase char_type if convertible, else __c.

Referenced by std::time_get< _CharT, _InIter >::get().

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widen — one char up 🫶

template<typename _CharT> char_type std::__ctype_abstract_base< _CharT >::widen (char __c) const

[inline], [inherited]

Widen char to char_type. This function converts the char argument to char_type using the simplest reasonable transformation. It does so by returning ctype<char_type>::do_widen(c).

Note: this is not what you want for codepage conversions. See codecvt for that. 🙈

Parameters

• __c — the char to convert.

Returns

The converted char_type.

Referenced by std::money_get< _CharT, _InIter >::do_get(), std::time_get< _CharT, _InIter >::do_get(), std::money_put< _CharT, _OutIter >::do_put(), and std::time_put< _CharT, _OutIter >::do_put().

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widen — whole array, go 🌟

template<typename _CharT> const char * std::__ctype_abstract_base< _CharT >::widen (const char * __lo, const char * __hi, char_type * __to) const

[inline], [inherited]

Widen array to char_type. This function converts each char in the input to char_type using the simplest reasonable transformation. It does so by returning ctype<char_type>::do_widen(c).

Note: this is not what you want for codepage conversions. See codecvt for that. 🙈

Parameters

• __lo — pointer to start of range.
• __hi — pointer to end of range.
• __to — pointer to the destination array.

Returns

__hi.

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Member Data Documentation 🌈

id — the facet id 💅

template<typename _CharT> locale::id std::ctype< _CharT >::id

[static]

The facet id for ctype<char_type>. That's it, that's the whole vibe check. ⭐

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Author ✍️

Generated automatically by Doxygen for libstdc++ from the source code.

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okay bestie that's the whole page 💖 this one came straight out of the libstdc++ docs — it's page std::ctype< _CharT >(3) in the libstdc++ manual, so if you ever need to cite it, that's the flex. go convert some chars, you're doing amazing 🎀✨👑