module HTMLClassMerge::RegexIndex

Overview

Given a Regex, return an index of the first n characters, if the regex would match those first n characters, or nil. This means the Regex must be anchored at the start, contain only word chars for the first n characters, and not be a union at the top level.

This can be used to pre-filter a long list of regexs to only those that might match a given string

regex = /\Afoo-(bar|baz)\z/
RegexIndex.regex_index(regex)            # => "fo"
RegexIndex.regex_index(regex, 3)         # => "foo"
RegexIndex.regex_index(regex, 4)         # => "foo-"
RegexIndex.regex_index(regex, 5)         # => nil
RegexIndex.regex_index(regex, 3, "f")    # => nil
RegexIndex.regex_index(regex, 3, /[fo]/) # => "foo"
RegexIndex.regex_index(regex, 4, /[fo]/) # => nil

Extended Modules

• HTMLClassMerge::RegexIndex

Direct including types

• HTMLClassMerge::GroupRegistry

Defined in:

html_class_merge/regex_index.cr

Instance Method Summary

• #regex_index(regex : Regex, n = 2, char = /[\w-]/) : String | Nil

  return the index of the first n characters, if the regex would match only those n characters, or nil

Instance Method Detail