Compile time regular expressions v3
Fast compile-time regular expressions with support for matching/searching/capturing during compile-time or runtime.
You can use the single header version from directory single-header. This header can be regenerated with make single-header. If you are using cmake, you can add this directory as subdirectory and link to target ctre.
More info at compile-time.re
What this library can do
ctre::match<"REGEX">(subject); // C++20
"REGEX"_ctre.match(subject); // C++17 + N3599 extension- Matching
- Searching (
searchorstarts_with) - Capturing content (named captures are supported too)
- Back-Reference (\g{N} syntax, and \1...\9 syntax too)
- Multiline support (with
multi_) functions - Unicode properties and UTF-8 support
The library is implementing most of the PCRE syntax with a few exceptions:
- atomic groups
- callouts
- comments
- conditional patterns
- control characters (
\cX) - match point reset (
\K) - named characters
- octal numbers
- options / modes
- subroutines
- unicode grapheme cluster (
\X)
More documentation on pcre.org.
Unknown character escape behaviour
Not all escaped characters are automatically inserted as self, behaviour of the library is escaped characters are with special meaning, unknown escaped character is a syntax error.
Explicitly allowed character escapes which insert only the character are:
\-\"\<\>
Basic API
This is approximated API specification from a user perspective (omitting constexpr and noexcept which are everywhere, and using C++20 syntax even the API is C++17 compatible):
// look if whole input matches the regex:
template <fixed_string regex> auto ctre::match(auto Range &&) -> regex_results;
template <fixed_string regex> auto ctre::match(auto First &&, auto Last &&) -> regex_results;
// look if input contains match somewhere inside of itself:
template <fixed_string regex> auto ctre::search(auto Range &&) -> regex_results;
template <fixed_string regex> auto ctre::search(auto First &&, auto Last &&) -> regex_results;
// check if input starts with match (but doesn't need to match everything):
template <fixed_string regex> auto ctre::starts_with(auto Range &&) -> regex_results;
template <fixed_string regex> auto ctre::starts_with(auto First &&, auto Last &&) -> regex_results;
// result type is deconstructible into a structured bindings
template <...> struct regex_results {
operator bool() const; // if it's a match
auto to_view() const -> std::string_view; // also view()
auto to_string() const -> std::string; // also str()
operator std::string_view() const; // also supports all char variants
explicit operator std::string() const;
// also size(), begin(), end(), data()
size_t count() const; // number of captures
template <size_t Id> const captured_content & get() const; // provide specific capture, whole regex_results is implicit capture 0
};Range outputing API
// search for regex in input and return each occurence, ignoring rest:
template <fixed_string regex> auto ctre::range(auto Range &&) -> range of regex_result;
template <fixed_string regex> auto ctre::range(auto First &&, auto Last &&) -> range of regex_result;
// return range of each match, stopping at something which can't be matched
template <fixed_string regex> auto ctre::tokenize(auto Range &&) -> range of regex_result;
template <fixed_string regex> auto ctre::tokenize(auto First &&, auto Last &&) -> range of regex_result;
// return parts of the input splited by the regex, returning it as part of content of the implicit zero capture (other captures are not changed, you can use it to access how the values were splitted):
template <fixed_string regex> auto ctre::split(auto Range &&) -> regex_result;
template <fixed_string regex> auto ctre::split(auto First &&, auto Last &&) -> range of regex_result;Functors
All the functions (ctre::match, ctre::search, ctre::starts_with, ctre::range, ctre::tokenize, ctre::split) are functors and can be used without parenthesis:
auto matcher = ctre::match<"regex">;
if (matcher(input)) ...Possible subjects (inputs)
std::string-like objects (std::string_viewor your own string if it's providingbegin/endfunctions with forward iterators)- pairs of forward iterators
Unicode support
To enable you need to include:
<ctre-unicode.hpp>- or
<ctre.hpp>and<unicode-db.hpp>
Otherwise you will get missing symbols if you try to use the unicode support without enabling it.
Supported compilers
- clang 6.0+ (template UDL, C++17 syntax)
- xcode clang 10.0+ (template UDL, C++17 syntax)
- clang 12.0+ (C++17 syntax, C++20 cNTTP syntax)
- gcc 8.0+ (template UDL, C++17 syntax)
- gcc 9.0+ (C++17 & C++20 cNTTP syntax)
- MSVC 15.8.8+ (C++17 syntax only) (semi-supported, I don't have windows machine)
Template UDL syntax
The compiler must support extension N3599, for example as GNU extension in gcc (not in GCC 9.1+) and clang.
constexpr auto match(std::string_view sv) noexcept {
using namespace ctre::literals;
return "h.*"_ctre.match(sv);
}If you need extension N3599 in GCC 9.1+, you can't use -pedantic. Also, you need to define macro CTRE_ENABLE_LITERALS.
C++17 syntax
You can provide a pattern as a constexpr ctll::fixed_string variable.
static constexpr auto pattern = ctll::fixed_string{ "h.*" };
constexpr auto match(std::string_view sv) noexcept {
return ctre::match<pattern>(sv);
}(this is tested in MSVC 15.8.8)
C++20 syntax
Currently, the only compiler which supports cNTTP syntax ctre::match<PATTERN>(subject) is GCC 9+.
constexpr auto match(std::string_view sv) noexcept {
return ctre::match<"h.*">(sv);
}Examples
Extracting number from input
std::optional<std::string_view> extract_number(std::string_view s) noexcept {
if (auto m = ctre::match<"[a-z]+([0-9]+)">(s)) {
return m.get<1>().to_view();
} else {
return std::nullopt;
}
}Extracting values from date
struct date { std::string_view year; std::string_view month; std::string_view day; };
std::optional<date> extract_date(std::string_view s) noexcept {
using namespace ctre::literals;
if (auto [whole, year, month, day] = ctre::match<"(\\d{4})/(\\d{1,2})/(\\d{1,2})">(s); whole) {
return date{year, month, day};
} else {
return std::nullopt;
}
}
//static_assert(extract_date("2018/08/27"sv).has_value());
//static_assert((*extract_date("2018/08/27"sv)).year == "2018"sv);
//static_assert((*extract_date("2018/08/27"sv)).month == "08"sv);
//static_assert((*extract_date("2018/08/27"sv)).day == "27"sv);Using captures
auto result = ctre::match<"(?<year>\\d{4})/(?<month>\\d{1,2})/(?<day>\\d{1,2})">(s);
return date{result.get<"year">(), result.get<"month">, result.get<"day">};
// or in C++ emulation, but the object must have a linkage
static constexpr ctll::fixed_string year = "year";
static constexpr ctll::fixed_string month = "month";
static constexpr ctll::fixed_string day = "day";
return date{result.get<year>(), result.get<month>, result.get<day>};
// or use numbered access
// capture 0 is the whole match
return date{result.get<1>(), result.get<2>, result.get<3>};Lexer
enum class type {
unknown, identifier, number
};
struct lex_item {
type t;
std::string_view c;
};
std::optional<lex_item> lexer(std::string_view v) noexcept {
if (auto [m,id,num] = ctre::match<"([a-z]+)|([0-9]+)">(v); m) {
if (id) {
return lex_item{type::identifier, id};
} else if (num) {
return lex_item{type::number, num};
}
}
return std::nullopt;
}Range over input
This support is preliminary, probably the API will be changed.
auto input = "123,456,768"sv;
for (auto match: ctre::range<"([0-9]+),?">(input)) {
std::cout << std::string_view{match.get<0>()} << "\n";
}Unicode
#include <ctre-unicode.hpp>
#include <iostream>
// needed if you want to output to the terminal
std::string_view cast_from_unicode(std::u8string_view input) noexcept {
return std::string_view(reinterpret_cast<const char *>(input.data()), input.size());
}
int main()
{
using namespace std::literals;
std::u8string_view original = u8"Tu es un génie"sv;
for (auto match : ctre::range<"\\p{Letter}+">(original))
std::cout << cast_from_unicode(match) << std::endl;
return 0;
}Running tests (for developers)
Just run make in root of this project.