Compile time regular expressions v2
Fast compile-time regular expression with support for matching/searching/capturing in compile-time or runtime.
You can use single header version from directory single-header. This header can be regenerated with make single-header.
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
- Capturing content (named captures are supported too)
- Back-Reference (\g{N} syntax, and \1...\9 syntax too)
The library is implementing most of the PCRE syntax with a few exceptions:
- atomic groups
- boundaries other than
^$ - callouts
- character properties
- comments
- conditional patterns
- control characters (
\cX) - horizontal / vertical character classes (
\h\H\v\V) - match point reset (
\K) - named characters
- octal numbers
- options / modes
- subroutines
- unicode grapheme cluster (
\X)
More documentation on pcre.org.
What can be subject (input)?
std::string-like object (std::string_viewor your own string if it's providingbegin/endfunctions with forward iterators)- pair of forward iterators
Supported compilers
- clang 6.0+ (template UDL, C++17 syntax)
- xcode clang 10.0+ (template UDL, C++17 syntax)
- gcc 7.4+ (template UDL, C++17 syntax)
- gcc 9.0+ (C++17 & C++20 cNTTP syntax)
- MSVC 15.8.8+ (C++17 syntax only)
Template UDL syntax
Compiler must support N3599 extension, 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 N3599 extension in GCC 9.1+ you can't use -pedantic mode and define macro CTRE_ENABLE_LITERALS.
C++17 syntax
You can provide 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 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);
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 and 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";
}