Class: RegexpExamples::ChargroupParser

Inherits:
Object
  • Object
show all
Defined in:
lib/regexp-examples/chargroup_parser.rb

Overview

A “sub-parser”, for char groups in a regular expression Some examples of what this class needs to parse:

abc

  • plain characters

a-z

  • ranges

nbd

  • escaped characters (which may represent character sets)

^abc

  • negated group

[a]

  • sub-groups (should match “a”, “b” or “c”)

[:lower:]

  • POSIX group

[a-f]&&

  • set intersection (should match “d”, “f” or “f”)

[^:alpha:]&&a-c

  • all of the above!!!! (should match “n”)

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(regexp_string, is_sub_group: false) ⇒ ChargroupParser

Returns a new instance of ChargroupParser.



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# File 'lib/regexp-examples/chargroup_parser.rb', line 14

def initialize(regexp_string, is_sub_group: false)
  @regexp_string = regexp_string
  @is_sub_group = is_sub_group
  @current_position = 0
  parse
end

Instance Attribute Details

#regexp_string ⇒ Object (readonly)

Returns the value of attribute regexp_string.



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# File 'lib/regexp-examples/chargroup_parser.rb', line 13

def regexp_string
  @regexp_string
end

Instance Method Details

#length ⇒ Object 



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# File 'lib/regexp-examples/chargroup_parser.rb', line 43

def length
  @current_position
end

#parse ⇒ Object 



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# File 'lib/regexp-examples/chargroup_parser.rb', line 21

def parse
  @charset = []
  @negative = false
  parse_first_chars
  until next_char == ']'
    case next_char
    when '['
      parse_sub_group_concat
    when '-'
      parse_after_hyphen
    when '&'
      parse_after_ampersand
    else
      @charset.concat parse_checking_backlash
      @current_position += 1
    end
  end

  @charset.uniq!
  @current_position += 1 # To account for final "]"
end

#result ⇒ Object 



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# File 'lib/regexp-examples/chargroup_parser.rb', line 47

def result
  @negative ? (CharSets::Any - @charset) : @charset
end