Skip to content
Topaz6.0 · Before release
Download

Search documentation

Specification 6.0 · Not released · Tested product 5.21.3

Use arrow keys to choose a result. Press Enter to open.

Type an API name, diagnostic number, rule, or project topic.

    Library · std.regex

    Regex.isMatch

    Reports whether a leftmost-first search finds a match anywhere in the input.

    isMatch(text: string) -> bool
    Module
    std.regex
    Receiver
    Regex
    Minimum arity
    1
    Maximum arity
    1

    Declaration and parameters

    Link

    Availability

    Included by default: Pending

    Import std.regex in language mode 5.21.

    The current compiler selects std/regex.tpz for this language mode. Availability in other released editions and inclusion in each installed distribution are Pending.

    Source evidence

    Receiver

    Regex

    Parameter constraints

    Additional contracts are Pending.

    Regex.isMatch reports whether a match exists anywhere in the input. Regex.find returns Some containing the first match or None() when no match exists. Regex.findAll returns every nonoverlapping match in search order and returns an empty array when no match exists.

    Search begins at the earliest Unicode scalar boundary that permits the complete pattern to match. At that position alternatives are tried in pattern order. Greedy repetitions prefer more scalars and lazy repetitions prefer fewer scalars while still allowing the rest of the pattern to match.

    After a nonempty match, findAll resumes at its exclusive end. After an empty match, it resumes at the next Unicode scalar boundary. An empty match directly at the end of the preceding nonempty match is skipped and search advances to the next scalar boundary.

    An empty pattern visits every scalar boundary, including both ends. The empty input has one boundary and produces one empty match for an empty pattern. Matching never splits the UTF-8 bytes of a scalar.

    Regex.split and Regex.replaceAll use the same ordered match sequence as findAll. Repeated calls start a new search and do not retain a cursor. The input string and compiled pattern are unchanged.

    The receiver is evaluated once before the positional arguments, which are evaluated once from left to right. Search does not invoke user callbacks or access external state. No match is an ordinary result and does not produce a diagnostic.

    Related rule: Search from the left and advance through nonoverlapping matches

    Result

    Additional contracts are Pending.

    The declared result type is bool.

    Effects

    Pending

    Failures

    Pending

    Result and effects

    Link

    Reports whether a leftmost-first search finds a match anywhere in the input.

    Resolved contracts

    Link

    Related entries

    Link

    std.regex

    Link
    Ruletopaz.stdlib.contract.regex-search.rule

    Search from the left and advance through nonoverlapping matches

    Regex.isMatch reports whether a match exists anywhere in the input. Regex.find returns Some containing the first match or None() when no match exists. Regex.findAll returns every nonoverlapping match in search order and returns an empty array when no match exists.

    Search begins at the earliest Unicode scalar boundary that permits the complete pattern to match. At that position alternatives are tried in pattern order. Greedy repetitions prefer more scalars and lazy repetitions prefer fewer scalars while still allowing the rest of the pattern to match.

    After a nonempty match, findAll resumes at its exclusive end. After an empty match, it resumes at the next Unicode scalar boundary. An empty match directly at the end of the preceding nonempty match is skipped and search advances to the next scalar boundary.

    An empty pattern visits every scalar boundary, including both ends. The empty input has one boundary and produces one empty match for an empty pattern. Matching never splits the UTF-8 bytes of a scalar.

    Regex.split and Regex.replaceAll use the same ordered match sequence as findAll. Repeated calls start a new search and do not retain a cursor. The input string and compiled pattern are unchanged.

    The receiver is evaluated once before the positional arguments, which are evaluated once from left to right. Search does not invoke user callbacks or access external state. No match is an ordinary result and does not produce a diagnostic.

    Why

    One ordered match sequence makes searching, splitting, and replacement agree. Advancing after an empty match ensures progress without splitting a Unicode scalar. Boolean search is distinct from extracting Match data and does not introduce regex membership through the in operator.

    Examples Choose the first successful alternative at the leftmost positionChoose a group alternative that allows the complete pattern to matchReturn nonoverlapping matches in input orderVisit each boundary for an empty pattern and the empty inputSkip an empty match directly after a nonempty matchReturn no match after scanning a longer valid input

    Source evidence

    Choose the first successful alternative at the leftmost position

    Link

    run · running · Verification: not-run

    main.tpzChoose the first successful alternative at the leftmost positionOpen in Playground
    1. import std.regex { Regex }
    2. import std.io
    4. match (Regex.compile("a|ab")) {
    5. case Ok(pattern) => {
    6. match (pattern.find("zab")) {
    7. case Some(found) => io.writeLine("{found.start}:{found.end}:{found.text}")
    8. case None() => io.writeLine("no match")
    9. }
    10. let present = pattern.isMatch("zab")
    11. let absent = pattern.isMatch("zzz")
    12. io.writeLine("{present}:{absent}")
    13. match (pattern.find("zzz")) {
    14. case None() => io.writeLine("none")
    15. case Some(_) => io.writeLine("present")
    16. }
    17. let matches = pattern.findAll("zzz")
    18. io.writeLine("{matches.length}")
    19. }
    20. case Err(_) => io.writeLine("compile failed")
    21. }
    Expected outputexit 0
    1:2:a
true:false
none
0
    $ topaz run main.tpz · target product 5.21.3
    Expected result

    Expected result

    Execution completes. Exit code 0.

    No stderr.

    Expected stdout
    1. 1:2:a
    2. true:false
    3. none
    4. 0

    This exact example has not been executed.

    Source evidence

    Choose a group alternative that allows the complete pattern to match

    Link

    run · running · Verification: not-run

    main.tpzChoose a group alternative that allows the complete pattern to matchOpen in Playground
    1. import std.regex { Regex }
    2. import std.io
    4. match (Regex.compile("(a|ab)c")) {
    5. case Ok(pattern) => {
    6. match (pattern.find("abc")) {
    7. case Some(found) => io.writeLine(found.text)
    8. case None() => io.writeLine("no match")
    9. }
    10. }
    11. case Err(_) => io.writeLine("compile failed")
    12. }
    Expected outputexit 0
    abc
    $ topaz run main.tpz · target product 5.21.3
    Expected result

    Expected result

    Execution completes. Exit code 0.

    No stderr.

    Expected stdout
    1. abc

    This exact example has not been executed.

    Source evidence

    Return nonoverlapping matches in input order

    Link

    run · running · Verification: not-run

    main.tpzReturn nonoverlapping matches in input orderOpen in Playground
    1. import std.regex { Regex }
    2. import std.io
    4. match (Regex.compile("aa")) {
    5. case Ok(pattern) => {
    6. for found in (pattern.findAll("aaaaa")) {
    7. io.writeLine("{found.start}:{found.end}:{found.text}")
    8. }
    9. }
    10. case Err(_) => io.writeLine("compile failed")
    11. }
    Expected outputexit 0
    0:2:aa
2:4:aa
    $ topaz run main.tpz · target product 5.21.3
    Expected result

    Expected result

    Execution completes. Exit code 0.

    No stderr.

    Expected stdout
    1. 0:2:aa
    2. 2:4:aa

    This exact example has not been executed.

    Source evidence

    Visit each boundary for an empty pattern and the empty input

    Link

    run · running · Verification: not-run

    main.tpzVisit each boundary for an empty pattern and the empty inputOpen in Playground
    1. import std.regex { Regex }
    2. import std.io
    4. match (Regex.compile("")) {
    5. case Ok(pattern) => {
    6. for found in (pattern.findAll("ab")) {
    7. io.writeLine("{found.start}:{found.end}")
    8. }
    9. io.writeLine("empty input")
    10. for found in (pattern.findAll("")) {
    11. io.writeLine("{found.start}:{found.end}")
    12. }
    13. }
    14. case Err(_) => io.writeLine("compile failed")
    15. }
    Expected outputexit 0
    0:0
1:1
2:2
empty input
0:0
    $ topaz run main.tpz · target product 5.21.3
    Expected result

    Expected result

    Execution completes. Exit code 0.

    No stderr.

    Expected stdout
    1. 0:0
    2. 1:1
    3. 2:2
    4. empty input
    5. 0:0

    This exact example has not been executed.

    Source evidence

    Skip an empty match directly after a nonempty match

    Link

    run · running · Verification: not-run

    main.tpzSkip an empty match directly after a nonempty matchOpen in Playground
    1. import std.regex { Regex }
    2. import std.io
    4. match (Regex.compile("a*")) {
    5. case Ok(pattern) => {
    6. for found in (pattern.findAll("ab")) {
    7. io.writeLine("{found.start}:{found.end}:{found.text}")
    8. }
    9. }
    10. case Err(_) => io.writeLine("compile failed")
    11. }
    Expected outputexit 0
    0:1:a
2:2:
    $ topaz run main.tpz · target product 5.21.3
    Expected result

    Expected result

    Execution completes. Exit code 0.

    No stderr.

    Expected stdout
    1. 0:1:a
    2. 2:2:

    This exact example has not been executed.

    Source evidence

    Return no match after scanning a longer valid input

    Link

    run · running · Verification: not-run

    main.tpzReturn no match after scanning a longer valid inputOpen in Playground
    1. import std.regex { Regex }
    2. import std.io
    4. let mut text = "a"
    5. for step in (0 .. 17) {
    6. text = text + text
    7. }
    8. match (Regex.compile("z")) {
    9. case Ok(pattern) => io.writeLine("{pattern.isMatch(text)}")
    10. case Err(_) => io.writeLine("compile failed")
    11. }
    Expected outputexit 0
    false
    $ topaz run main.tpz · target product 5.21.3
    Expected result

    Expected result

    Execution completes. Exit code 0.

    No stderr.

    Expected stdout
    1. false

    This exact example has not been executed.

    Source evidence

    Menu

    Download