predicate.hpp File Reference

Provides character predicates for tokenisation. More...

#include <seqan3/utility/char_operations/predicate_detail.hpp>

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Namespaces
namespace	seqan3
	The main SeqAn3 namespace.

Variables
Char predicates
Char predicates are function like objects that can be used to check if a character c fulfills certain constraints. SeqAn implements all predicates also available in the standard library and some more. Disjunction and Negation In contrast to the standard library (where the checks are implemented as functions), the functors in SeqAn can be joined efficiently, maintaining constant-time evaluation independent of the number of checks. Functors can be combined with the ||-operator or negated via the !-operator: // 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 <iostream> #include <seqan3/utility/char_operations/predicate.hpp> int main() { char chr{'1'}; constexpr auto my_cond = seqan3::is_char<'%'> || seqan3::is_digit; bool is_percent = my_cond(chr); std::cout << std::boolalpha << is_percent << '\n'; // true } Defining complex combinations and using them in e.g. input/output can increase speed significantly over checking multiple functions: we measured speed-ups of 10x for a single check and speed-ups of over 20x for complex combinations. Custom predicates seqan3::is_in_interval: Checks if the given character is within specified range of ASCII characters. seqan3::is_char: Checks if the character is equal to the specified ASCII character. seqan3::is_eof: Checks if a character is the end-of-file marker. Standard library predicates SeqAn offers the 12 predicates exactly as defined in the standard library except that we have introduced an underscore in the name to be consistent with our other naming. The following table lists the predefined character predicates and which constraints are associated with them. ASCII values characters is_cntrl is_print is_space is_blank is_graph is_punct is_alnum is_alpha is_upper is_lower is_digit is_xdigit decimal hexadecimal octal 0–8 \x0–\x8 \0–\10 control codes (NUL, etc.) ≠0 0 0 0 0 0 0 0 0 0 0 0 9 \x9 \11 tab (\t) ≠0 0 ≠0 ≠0 0 0 0 0 0 0 0 0 10–13 \xA–\xD \12–\15 whitespaces (\n, \v, \f, \r) ≠0 0 ≠0 0 0 0 0 0 0 0 0 0 14–31 \xE–\x1F \16–\37 control codes ≠0 0 0 0 0 0 0 0 0 0 0 0 32 \x20 \40 space 0 ≠0 ≠0 ≠0 0 0 0 0 0 0 0 0 33–47 \x21–\x2F \41–\57 !"#$%&'()*+,-./ 0 ≠0 0 0 ≠0 ≠0 0 0 0 0 0 0 48–57 \x30–\x39 \60–\71 0123456789 0 ≠0 0 0 ≠0 0 ≠0 0 0 0 ≠0 ≠0 58–64 \x3A–\x40 \72–\100 :;<=>?@ 0 ≠0 0 0 ≠0 ≠0 0 0 0 0 0 0 65–70 \x41–\x46 \101–\106 ABCDEF 0 ≠0 0 0 ≠0 0 ≠0 ≠0 ≠0 0 0 ≠0 71–90 \x47–\x5A \107–\132 GHIJKLMNOP QRSTUVWXYZ 0 ≠0 0 0 ≠0 0 ≠0 ≠0 ≠0 0 0 0 91–96 \x5B–\x60 \133–\140 []^_` 0 ≠0 0 0 ≠0 ≠0 0 0 0 0 0 0 97–102 \x61–\x66 \141–\146 abcdef 0 ≠0 0 0 ≠0 0 ≠0 ≠0 0 ≠0 0 ≠0 103–122 \x67–\x7A \147–\172 ghijklmnop qrstuvwxyz 0 ≠0 0 0 ≠0 0 ≠0 ≠0 0 ≠0 0 0 123–126 \x7B–\x7E \172–\176 {|}~ 0 ≠0 0 0 ≠0 ≠0 0 0 0 0 0 0 127 \x7F \177 backspace character (DEL) ≠0 0 0 0 0 0 0 0 0 0 0 0
constexpr auto	seqan3::is_alnum = is_in_interval<'0', '9'> || is_in_interval<'A', 'Z'> || is_in_interval<'a', 'z'>
	Checks whether c is a alphanumeric character.
constexpr auto	seqan3::is_alpha = is_in_interval<'A', 'Z'> || is_in_interval<'a', 'z'>
	Checks whether c is a alphabetical character.
constexpr auto	seqan3::is_blank = is_char<'\t'> || is_char<' '>
	Checks whether c is a blank character.
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_digit = is_in_interval<'0', '9'>
	Checks whether c is a digital character.
constexpr auto	seqan3::is_eof = is_char<EOF>
	Checks whether a given letter is equal to the EOF constant defined in <cstdio>.
constexpr auto	seqan3::is_graph = is_in_interval<'!', '~'>
	Checks whether c is a graphic character.
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.
constexpr auto	seqan3::is_lower = is_in_interval<'a', 'z'>
	Checks whether c is a lower case character.
constexpr auto	seqan3::is_print = is_in_interval<' ', '~'>
	Checks whether c is a printable character.
constexpr auto	seqan3::is_punct
	Checks whether c is a punctuation character.
constexpr auto	seqan3::is_space = is_in_interval<'\t', '\r'> || is_char<' '>
	Checks whether c is a space character.
constexpr auto	seqan3::is_upper = is_in_interval<'A', 'Z'>
	Checks whether c is a upper case 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.

Detailed Descriptionno-api

Provides character predicates for tokenisation.

Author

Rene Rahn <rene.rahn AT fu-berlin.de>

Hannes Hauswedell <hannes.hauswedell AT fu-berlin.de>