gleam/regex

This module contains regular expression matching functions for strings. The matching algorithms of the library are based on the PCRE library, but not all of the PCRE library is interfaced and some parts of the library go beyond what PCRE offers. Currently PCRE version 8.40 (release date 2017-01-11) is used.

Types

CompileError

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The full string of the match. The byte index of the match in the original string. A Regex can have subpatterns, sup-parts that are in parentheses. When a regular expression fails to compile:

pub type CompileError {
  CompileError(error: String, byte_index: Int)
}

Constructors

CompileError(error: String, byte_index: Int)

Match

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The details about a particular match:

pub type Match {
  Match(
    content: String,
    byte_index: Int,
    submatches: List(Option(String)),
  )
}

Constructors

Match(
  content: String,
  byte_index: Int,
  submatches: List(Option(String)),
)

Options

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The problem encountered that caused the compilation to fail The byte index into the string to where the problem was found

pub type Options {
  Options(case_insensitive: Bool, multi_line: Bool)
}

Constructors

Options(case_insensitive: Bool, multi_line: Bool)

Regex

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pub external type Regex

Functions

check

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pub external fn check(with: Regex, content: String) -> Bool

Returns a boolean indicating whether there was a match or not.

Examples

> assert Ok(re) = from_string("^f.o.?")
> check(with: re, content: "foo")
True

> check(with: re, content: "boo")
False

compile

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pub external fn compile(
  String,
  with: Options,
) -> Result(Regex, CompileError)

Creates a Regex with some additional options.

Examples

> let options = Options(case_insensitive: False, multi_line: True)
> assert Ok(re) = compile("^[0-9]", with: options)
> match(re, "abc\n123")
True

> let options = Options(case_insensitive: True, multi_line: False)
> assert Ok(re) = compile("[A-Z]", with: options)
> match(re, "abc123")
True

from_string

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pub fn from_string(
  pattern: String,
) -> Result(Regex, CompileError)

Creates a new Regex.

Examples

> assert Ok(re) = from_string("[0-9]")
> match(re, "abc123")
True

> match(re, "abcxyz")
False

> from_string("[0-9")
Error(
  CompileError(
    error: "missing terminating ] for character class",
    byte_index: 4
  )
)

scan

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pub external fn scan(with: Regex, content: String) -> List(Match)

Collects all matches of the regular expression.

Examples

> assert Ok(re) = regex.from_string("[oi]n a (\\w+)")
> regex.scan(with: re, content: "I am on a boat in a lake.")
[
  Match(
    content: "on a boat",
    byte_index: 5,
    submatches: [Some("boat")]
  ),
  Match(
    content: "in a lake",
    byte_index: 15,
    submatches: [Some("lake")]
  )
]

split

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pub external fn split(
  with: Regex,
  content: String,
) -> List(String)

Splits a string

Examples

> assert Ok(re) = from_string(" *, *")
> split(with: re, content: "foo,32, 4, 9  ,0")
["foo", "32", "4", "9", "0"]