Regex object holds regular expression pattern in compiled form.
Exception object thrown in case of errors during regex compilation.
A StaticRegex is Regex object that contains D code specially generated at compile-time to speed up matching.
Compile regular expression using CTFE and generate optimized native machine code for matching it.
Start matching of input to regex pattern re, using traditional backtracking matching scheme.
A range that lazily produces a string output escaped to be used inside of a regular expression.
Start matching input to regex pattern re, using Thompson NFA matching scheme.
Initiate a search for all non-overlapping matches to the pattern re in the given input. The result is a lazy range of matches generated as they are encountered in the input going left to right.
Find the first (leftmost) slice of the input that matches the pattern re. This function picks the most suitable regular expression engine depending on the pattern properties.
Compile regular expression pattern for the later execution.
Old API for replacement, operation depends on flags of pattern re. With "g" flag it performs the equivalent of replaceAll otherwise it works the same as replaceFirst.
Construct a new string from input by replacing all of the fragments that match a pattern re with a string generated from the match according to the format specifier.
This is a general replacement tool that construct a new string by replacing matches of pattern re in the input. Unlike the other overload there is no format string instead captures are passed to to a user-defined functor fun that returns a new string to use as replacement.
A variation on replaceAll that instead of allocating a new string on each call outputs the result piece-wise to the sink. In particular this enables efficient construction of a final output incrementally.
Construct a new string from input by replacing the first match with a string generated from it according to the format specifier.
This is a general replacement tool that construct a new string by replacing matches of pattern re in the input. Unlike the other overload there is no format string instead captures are passed to to a user-defined functor fun that returns a new string to use as replacement.
A variation on replaceFirst that instead of allocating a new string on each call outputs the result piece-wise to the sink. In particular this enables efficient construction of a final output incrementally.
An eager version of splitter that creates an array with splitted slices of input.
Splits a string r using a regular expression pat as a separator.
Captures object contains submatches captured during a call to match or iteration over RegexMatch range.
A regex engine state, as returned by match family of functions.
Splits a string r using a regular expression pat as a separator.
The general usage guideline is to keep regex complexity on the side of simplicity, as its capabilities reside in purely character-level manipulation. As such it's ill-suited for tasks involving higher level invariants like matching an integer number bounded in an [a,b] interval. Checks of this sort of are better addressed by additional post-processing.
The basic syntax shouldn't surprise experienced users of regular expressions. For an introduction to std.regex see a short tour of the module API and its abilities.
There are other web resources on regular expressions to help newcomers, and a good reference with tutorial can easily be found.
This library uses a remarkably common ECMAScript syntax flavor with the following extensions:
std.regex operates on codepoint level, 'character' in this table denotes a single Unicode codepoint.
| Pattern element | Semantics |
| Atoms | Match single characters |
| any character except [{|*+?()^$ | Matches the character itself. |
| . | In single line mode matches any character. Otherwise it matches any character except '\n' and '\r'. |
| class | Matches a single character that belongs to this character class. |
| [^class] | Matches a single character that does not belong to this character class. |
| \cC | Matches the control character corresponding to letter C |
| \xXX | Matches a character with hexadecimal value of XX. |
| \uXXXX | Matches a character with hexadecimal value of XXXX. |
| \U00YYYYYY | Matches a character with hexadecimal value of YYYYYY. |
| \f | Matches a formfeed character. |
| \n | Matches a linefeed character. |
| \r | Matches a carriage return character. |
| \t | Matches a tab character. |
| \v | Matches a vertical tab character. |
| \d | Matches any Unicode digit. |
| \D | Matches any character except Unicode digits. |
| \w | Matches any word character (note: this includes numbers). |
| \W | Matches any non-word character. |
| \s | Matches whitespace, same as \p{White_Space}. |
| \S | Matches any character except those recognized as \s. |
| \\\\ | Matches \ character. |
| \c where c is one of [|*+?() | Matches the character c itself. |
| \p{PropertyName} | Matches a character that belongs to the Unicode PropertyName set. Single letter abbreviations can be used without surrounding {,}. |
| \P{PropertyName} | Matches a character that does not belong to the Unicode PropertyName set. Single letter abbreviations can be used without surrounding {,}. |
| \p{InBasicLatin} | Matches any character that is part of the BasicLatin Unicode block. |
| \P{InBasicLatin} | Matches any character except ones in the BasicLatin Unicode block. |
| \p{Cyrillic} | Matches any character that is part of Cyrillic script. |
| \P{Cyrillic} | Matches any character except ones in Cyrillic script. |
| Quantifiers | Specify repetition of other elements |
| * | Matches previous character/subexpression 0 or more times. Greedy version - tries as many times as possible. |
| *? | Matches previous character/subexpression 0 or more times. Lazy version - stops as early as possible. |
| + | Matches previous character/subexpression 1 or more times. Greedy version - tries as many times as possible. |
| +? | Matches previous character/subexpression 1 or more times. Lazy version - stops as early as possible. |
| ? | Matches previous character/subexpression 0 or 1 time. Greedy version - tries as many times as possible. |
| ?? | Matches previous character/subexpression 0 or 1 time. Lazy version - stops as early as possible. |
| {n} | Matches previous character/subexpression exactly n times. |
| {n,} | Matches previous character/subexpression n times or more. Greedy version - tries as many times as possible. |
| {n,}? | Matches previous character/subexpression n times or more. Lazy version - stops as early as possible. |
| {n,m} | Matches previous character/subexpression n to m times. Greedy version - tries as many times as possible, but no more than m times. |
| {n,m}? | Matches previous character/subexpression n to m times. Lazy version - stops as early as possible, but no less then n times. |
| Other | Subexpressions & alternations |
| (regex) | Matches subexpression regex, saving matched portion of text for later retrieval. |
| (?#comment) | An inline comment that is ignored while matching. |
| (?:regex) | Matches subexpression regex, not saving matched portion of text. Useful to speed up matching. |
| A|B | Matches subexpression A, or failing that, matches B. |
| (?P<name>regex) | Matches named subexpression regex labeling it with name 'name'. When referring to a matched portion of text, names work like aliases in addition to direct numbers. |
| Assertions | Match position rather than character |
| ^ | Matches at the beginning of input or line (in multiline mode). |
| $ | Matches at the end of input or line (in multiline mode). |
| \b | Matches at word boundary. |
| \B | Matches when not at word boundary. |
| (?=regex) | Zero-width lookahead assertion. Matches at a point where the subexpression regex could be matched starting from the current position. |
| (?!regex) | Zero-width negative lookahead assertion. Matches at a point where the subexpression regex could not be matched starting from the current position. |
| (?<=regex) | Zero-width lookbehind assertion. Matches at a point where the subexpression regex could be matched ending at the current position (matching goes backwards). |
| (?<!regex) | Zero-width negative lookbehind assertion. Matches at a point where the subexpression regex could not be matched ending at the current position (matching goes backwards). |
| Pattern element | Semantics |
| Any atom | Has the same meaning as outside of a character class, except for ] which must be written as \\] |
| a-z | Includes characters a, b, c, ..., z. |
| |b, [a--b], [a~~b], [a&&b] | Where a, b are arbitrary classes, means union, set difference, symmetric set difference, and intersection respectively. Any sequence of character class elements implicitly forms a union. |
| Flag | Semantics |
| g | Global regex, repeat over the whole input. |
| i | Case insensitive matching. |
| m | Multi-line mode, match ^, $ on start and end line separators as well as start and end of input. |
| s | Single-line mode, makes . match '\n' and '\r' as well. |
| x | Free-form syntax, ignores whitespace in pattern, useful for formatting complex regular expressions. |
This library provides full Level 1 support* according to UTS 18. Specifically:
*With exception of point 1.1.1, as of yet, normalization of input is expected to be enforced by user.
A set of functions in this module that do the substitution rely on a simple format to guide the process. In particular the table below applies to the format argument of replaceFirst and replaceAll.
The format string can reference parts of match using the following notation.
| Format specifier | Replaced by |
| $& | the whole match. |
| $` | part of input preceding the match. |
| $' | part of input following the match. |
| $$ | '$' character. |
| \c , where c is any character | the character c itself. |
| \\\\ | '\\' character. |
| $1 .. $99 | submatch number 1 to 99 respectively. |
All matches returned by pattern matching functionality in this library are slices of the original input. The notable exception is the replace family of functions that generate a new string from the input.
In cases where producing the replacement is the ultimate goal replaceFirstInto and replaceAllInto could come in handy as functions that avoid allocations even for replacement.
Copyright Dmitry Olshansky, 2011-
Regular expressions are a commonly used method of pattern matching on strings, with regex being a catchy word for a pattern in this domain specific language. Typical problems usually solved by regular expressions include validation of user input and the ubiquitous find & replace in text processing utilities.
Synopsis
Create a regex at runtime: $(RUNNABLE_EXAMPLE $(RUNNABLE_EXAMPLE_STDIN They met on 24/01/1970. 7/8/99 wasn't as hot as 7/8/2022. ) --- import std.regex; import std.stdio; // Print out all possible dd/mm/yy(yy) dates found in user input. auto r = regex(r"\b[0-9][0-9]?/[0-9][0-9]?/[0-9][0-9](?:[0-9][0-9])?\b"); foreach (line; stdin.byLine) { // matchAll() returns a range that can be iterated // to get all subsequent matches. foreach (c; matchAll(line, r)) writeln(c.hit); } --- ) Create a static regex at compile-time, which contains fast native code: $(RUNNABLE_EXAMPLE --- import std.regex; auto ctr = ctRegex!(`^.*/([^/]+)/?$`); // It works just like a normal regex: auto c2 = matchFirst("foo/bar", ctr); // First match found here, if any assert(!c2.empty); // Be sure to check if there is a match before examining contents! assert(c2[1] == "bar"); // Captures is a range of submatches: 0 = full match. --- ) Multi-pattern regex: $(RUNNABLE_EXAMPLE --- import std.regex; auto multi = regex([`\d+,\d+`, `([a-z]+):(\d+)`]); auto m = "abc:43 12,34".matchAll(multi); assert(m.front.whichPattern == 2); assert(m.front[1] == "abc"); assert(m.front[2] == "43"); m.popFront(); assert(m.front.whichPattern == 1); assert(m.front[0] == "12,34"); --- ) Captures and opCast!bool: $(RUNNABLE_EXAMPLE --- import std.regex; // The result of `matchAll/matchFirst` is directly testable with `if/assert/while`, // e.g. test if a string consists of letters only: assert(matchFirst("LettersOnly", `^\p{L}+$`)); // And we can take advantage of the ability to define a variable in the IfCondition: if (const captures = matchFirst("At l34st one digit, but maybe more...", `((\d)(\d*))`)) { assert(captures[2] == "3"); assert(captures[3] == "4"); assert(captures[1] == "34"); } --- )