Builtin Character Operations

Provides various operations on character types. More...

Collaboration diagram for Builtin Character Operations:

Char predicates
A set of function objects to check if a character from an input source fulfills certain characteristics.
template<uint8_t interval_first, uint8_t interval_last>
constexpr auto	seqan3::is_in_interval
	Checks whether a given letter is in the specified interval.
template<int char_v>
constexpr auto	seqan3::is_char
	Checks whether a given letter is the same as the template non-type argument.
constexpr auto	seqan3::is_cntrl = is_in_interval<'\0', static_cast<char>(31)> || is_char<static_cast<char>(127)>
	Checks whether c is a control character.
constexpr auto	seqan3::is_print = is_in_interval<' ', '~'>
	Checks whether c is a printable character.
constexpr auto	seqan3::is_space = is_in_interval<'\t', '\r'> || is_char<' '>
	Checks whether c is a space character.
constexpr auto	seqan3::is_blank = is_char<'\t'> || is_char<' '>
	Checks whether c is a blank character.
constexpr auto	seqan3::is_alpha = is_in_interval<'A', 'Z'> || is_in_interval<'a', 'z'>
	Checks whether c is a graphic character.
constexpr auto	seqan3::is_upper = is_in_interval<'A', 'Z'>
	Checks whether c is a upper case character.
constexpr auto	seqan3::is_lower = is_in_interval<'a', 'z'>
	Checks whether c is a lower case character.
constexpr auto	seqan3::is_digit = is_in_interval<'0', '9'>
	Checks whether c is a digital character.
constexpr auto	seqan3::is_xdigit = is_in_interval<'0', '9'> || is_in_interval<'A', 'F'> || is_in_interval<'a', 'f'>
	Checks whether c is a hexadecimal character.
constexpr auto	seqan3::is_eof = is_char<EOF>
	Checks whether a given letter is equal to the EOF constant defined in <cstdio>.

Detailed Description

Provides various operations on character types.

See also

Utility

Variable Documentation

is_alpha

auto seqan3::is_alpha = is_in_interval<'A', 'Z'> || is_in_interval<'a', 'z'>

inlineconstexpr

Checks whether c is a graphic character.

This function like object can be used to check if a character c is a graphic (has a graphical representation) character. For the standard ASCII character set, the following characters are graphic characters:

• digits (0123456789)
• uppercase letters (ABCDEFGHIJKLMNOPQRSTUVWXYZ)
• lowercase letters (abcdefghijklmnopqrstuvwxyz)
• punctuation characters (!"#$%&'()*+,-./:;<=>?@[]^_`{|}~)

Example

    static_assert(seqan3::is_graph('%'));

*/ inline constexpr auto is_graph = is_in_interval<'!', '~'>;

/*! Checks whether c is a punctuation character.

This function like object can be used to check if a character c is a punctuation character. For the standard ASCII character set, the following characters are punctuation characters:

• punctuation characters (!"#$%&'()*+,-./:;<=>?@[]^_`{|}~)

Example

    static_assert(seqan3::is_punct(':'));

*/ inline constexpr auto is_punct = is_in_interval<'!', '/'> || is_in_interval<':', '@'> || is_in_interval<'[', '`'> || is_in_interval<'{', '~'>;

/*! Checks whether c is a alphanumeric character.

This function like object can be used to check if a character c is a alphanumeric character. For the standard ASCII character set, the following characters are alphanumeric characters:

• digits (0123456789)
• uppercase letters (ABCDEFGHIJKLMNOPQRSTUVWXYZ)
• lowercase letters (abcdefghijklmnopqrstuvwxyz)

Example

    static_assert(seqan3::is_alnum('9'));

*/ inline constexpr auto is_alnum = is_in_interval<'0', '9'> || is_in_interval<'A', 'Z'> || is_in_interval<'a', 'z'>;

/*! Checks whether c is a alphabetical character.

This function like object can be used to check if a character c is a alphabetical character. For the standard ASCII character set, the following characters are alphabetical characters:

• uppercase letters (ABCDEFGHIJKLMNOPQRSTUVWXYZ)
• lowercase letters (abcdefghijklmnopqrstuvwxyz)

Example

    static_assert(seqan3::is_alpha('z'));

is_blank

auto seqan3::is_blank = is_char<'\t'> || is_char<' '>

inlineconstexpr

Checks whether c is a blank character.

This function like object can be used to check if a character c is a blank character. For the standard ASCII character set, the following characters are blank characters:

• horizontal tab ('\t')
• space (' ')

Example

    static_assert(seqan3::is_blank('\t'));

is_char

template<int char_v>

auto seqan3::is_char

inlineconstexpr

Checks whether a given letter is the same as the template non-type argument.

Template Parameters

char_v

The letter to compare against.

This function like object returns true if the argument is the same as the template argument, false otherwise.

Example

// SPDX-FileCopyrightText: 2006-2025 Knut Reinert & Freie Universität Berlin
// SPDX-FileCopyrightText: 2016-2025 Knut Reinert & MPI für molekulare Genetik
// SPDX-License-Identifier: CC0-1.0
 
#include <seqan3/utility/char_operations/predicate.hpp>
 
int main()
{
    seqan3::is_char<'C'>('C'); // returns true
 
    constexpr auto my_check = seqan3::is_char<'C'>;
    my_check('c'); // returns false, because case is different
}

is_cntrl

auto seqan3::is_cntrl = is_in_interval<'\0', static_cast<char>(31)> || is_char<static_cast<char>(127)>

inlineconstexpr

Checks whether c is a control character.

This function like object can be used to check if a character c is a control character. For the standard ASCII character set, control characters are those between ASCII codes 0x00 (NUL) and 0x1f (US) and 0x7f (DEL).

Example

    static_assert(seqan3::is_cntrl('\0'));

is_digit

auto seqan3::is_digit = is_in_interval<'0', '9'>

inlineconstexpr

Checks whether c is a digital character.

This function like object can be used to check if a character c is a digital character. For the standard ASCII character set, the following characters are digital characters:

• digits (0123456789)

Example

    static_assert(seqan3::is_digit('1'));

is_eof

auto seqan3::is_eof = is_char<EOF>

inlineconstexpr

Checks whether a given letter is equal to the EOF constant defined in <cstdio>.

This function like object returns true if the argument is equal to EOF, false otherwise.

Example

    static_assert(seqan3::is_eof(EOF));
    static_assert(!seqan3::is_eof('C'));

is_in_interval

template<uint8_t interval_first, uint8_t interval_last>

auto seqan3::is_in_interval

inlineconstexpr

Checks whether a given letter is in the specified interval.

Template Parameters

interval_first	The first character for which to return true.
interval_last	The last character (inclusive) for which to return true.

This function like object returns true for all characters in the given range, false otherwise.

Example

// SPDX-FileCopyrightText: 2006-2025 Knut Reinert & Freie Universität Berlin
// SPDX-FileCopyrightText: 2016-2025 Knut Reinert & MPI für molekulare Genetik
// SPDX-License-Identifier: CC0-1.0
 
#include <seqan3/utility/char_operations/predicate.hpp>
 
int main()
{
    seqan3::is_in_interval<'A', 'G'>('C'); // returns true
 
    constexpr auto my_check = seqan3::is_in_interval<'A', 'G'>;
    my_check('H'); // returns false
}

is_lower

auto seqan3::is_lower = is_in_interval<'a', 'z'>

inlineconstexpr

Checks whether c is a lower case character.

This function like object can be used to check if a character c is a lower case character. For the standard ASCII character set, the following characters are lower case characters:

• lowercase letters (abcdefghijklmnopqrstuvwxyz)

Example

    static_assert(seqan3::is_lower('a'));

is_print

auto seqan3::is_print = is_in_interval<' ', '~'>

inlineconstexpr

Checks whether c is a printable character.

This function like object can be used to check if a character c is a printable character. For the standard ASCII character set, printable characters are those between ASCII codes 0x20 (space) and 0x7E (~).

Example

    static_assert(seqan3::is_print(' '));

is_space

auto seqan3::is_space = is_in_interval<'\t', '\r'> || is_char<' '>

inlineconstexpr

Checks whether c is a space character.

This function like object can be used to check if a character c is a space character. For the standard ASCII character set, the following characters are space characters:

• horizontal tab ('\t')
• line feed ('\n')
• vertical tab ('\v')
• from feed ('\f')
• carriage return ('\r')
• space (' ')

Example

    static_assert(seqan3::is_space('\n'));

is_upper

auto seqan3::is_upper = is_in_interval<'A', 'Z'>

inlineconstexpr

Checks whether c is a upper case character.

This function like object can be used to check if a character c is a upper case character. For the standard ASCII character set, the following characters are upper case characters:

• uppercase letters (ABCDEFGHIJKLMNOPQRSTUVWXYZ)

Example

    static_assert(seqan3::is_upper('K'));

is_xdigit

auto seqan3::is_xdigit = is_in_interval<'0', '9'> || is_in_interval<'A', 'F'> || is_in_interval<'a', 'f'>

inlineconstexpr

Checks whether c is a hexadecimal character.

This function like object can be used to check if a character c is a hexadecimal character. For the standard ASCII character set, the following characters are hexadecimal characters:

• digits (0123456789)
• uppercase letters (ABCDEF)
• lowercase letters (abcdef)

Example

    static_assert(seqan3::is_xdigit('e'));