NAME

regex myr-regex

LIBRARY

regex

SYNOPSIS

use regex const compile : (re : byte[:] -> std.error(regex#, status)) const dbgcompile : (re : byte[:] -> std.error(regex#, status)) const free : (re : regex# -> void)
const exec : (re : regex#, str : byte[:] -> bool) const search : (re : regex#, str : byte[:] -> bool)

DESCRIPTION

The regex library provides functions for compiling and evaluating regular expressions, as described later in this document, or in myr-regex(7).

regex.compile will take a string describing a regex, and will attempt to compile it, returing `std.Success regex# if the regex is valid, and there were no error conditions encountered during compilation. If the compilation failed, `std.Failure regex.status will be returned, where regex.status is a failure code.

regex.dbgcompile is identical to regex.compile, however, it will print debugging information as it compiles, and each time the regex is evaluated.

regex.exec will take the regex passed to it, and evaluate it over the text provided, returning the `std.Some matches, or `std.None if there were no matches found. The matches must span the whole string.

regex.search is similar to regex.exec, but it will attempt to find a match somewhere within the string, instead of attempting to find a match spanning the whole string.

REGEX SYNTAX

The grammar used by libregex is below:

    regex       : altexpr
    altexpr     : catexpr ('|' altexpr)+
    catexpr     : repexpr (catexpr)+
    repexpr     : baseexpr[*+?]
    baseexpr    : literal
                | charclass
                | charrange
                | escaped
                | '.'
                | '^'
                | '$'
                | '(' regex ')'
    charclass   : see below
    charrange   : '[' (literal('-' literal)?)+']'

The following metacharacters have the meanings listed below:

Matches a single unicode character
^: Matches the beginning of a line. Does not consume any characters.
$: Matches the end of a line. Does not consume any characters.
*: Matches any number of repetitions of the preceding regex fragment.
*?: Reluctantly matches any number of repetitions of the preceding regex fragment.
+: Matches one or more repetitions of the preceding regex fragment.
+?: Reluctantly matches one or more repetitions of the preceding regex fragment.
?: Matches zero or one of the preceding regex fragment.

In order to match a literal metacharacter, it needs to be preceded by a '\' character.

The following character classes are supported:

\d: ASCII digits
\D: Negation of ASCII digits
\x: ASCII Hex digits
\X: Negation of ASCII Hex digits
\s: ASCII spaces
\S: Negation of ASCII spaces
\w: ASCII word characters
\W: Negation of ASCII word characters
\h: ASCII whitespace characters
\H: Negation of ASCII whitespace characters
\pX, \p{X}: Characters with unicode property 'X'
\PX, \P{X}: Negation of characters with unicode property 'X'

Unicode properties that are supported are listed below:

L, Letter

Unicode letter property

Lu, Uppercase_Letter

Uppercase letter unicode property

Ll, Lowercase_Letter

Lowercase letter unicode property

Lt, Titlecase_Letter

Titlecase letter unicode property

N, Number

Number unicode property

Z, Separator

Any separator character unicode property

Zs, Space_Separator

Space separator unicode property

EXAMPLE

        use std
        use regex
        const main = {
            var i
            match regex.compile(pat)
            | `std.Ok re:
                    match regex.exec(re, text)
                    | `std.Some matches:
                            for i = 0; i < matches.len; i++
                                std.put("Match {}: {}0, i, matches[i])
                            ;;
                    | `std.None: std.put("Text did not match0)
                    ;;
            | `std.Err err:
                    std.put("failed to compile regex")
            ;;
        }

FILES

The source code for this compiler is available from git://git.eigenstate.org/git/ori/libregex.git

BUGS

This code is insufficiently tested.

This code does not support all of the regex features that one would expect.