Non capture and named capture groups implemeneted

Warning: Not yet added named capture group backreference code

Author: tom-lord

README.md

@@ -30,14 +30,14 @@ or a huge number of possible matches, such as `/.\w/`, then only a subset of the
 * Character sets (inluding ranges and negation!), e.g. `/[abc]/`, `/[A-Z0-9]/`, `/[^a-z]/`
 * Escaped characters, e.g. `/\n/`, `/\w/`, `/\D/` (and so on...)
 * Capture groups, and backreferences(!!), e.g. `/(this|that) \1/`
+* Named capture groups, e.g. `(?<name>bar)/`(Warning: Named capture group backreferences not yet implemented!)
+* Non-capture groups, e.g. `/(?:foo)/`
 * Arbitrarily complex combinations of all the above!
 
 ## Not-Yet-Supported syntax
 
 I plan to add the following features to the gem (in order of most -> least likely), but have not yet got round to it:
 
-* Non-capture groups, e.g. `/(?:foo)/`
-* Named capture groups, e.g. `(?<name>bar)/`
 * Throw exceptions if illegal syntax (see below) is used
 * POSIX bracket expressions, e.g. `/[[:alnum:]]/`, `/[[:space:]]/`
 * Options, e.g. `/pattern/i`, `/foo.*bar/m`

lib/regexp-examples/parser.rb

@@ -45,7 +45,7 @@ def parse_group(repeaters)
     def parse_after_backslash_group
       @current_position += 1
       case
-      when regexp_string[@current_position..-1] =~ /^(\d+)/
+      when rest_of_string =~ /\A(\d+)/
         group = parse_backreference_group($&)
       when BackslashCharMap.keys.include?(regexp_string[@current_position])
         group = CharGroup.new(
@@ -79,11 +79,25 @@ def parse_repeater(group)
     def parse_multi_group
       @current_position += 1
       @num_groups += 1
-      this_group_num = @num_groups
+      group_id = nil # init
+      rest_of_string.match(/\A(\?)?(:|!|=|<(!|=|[^!=][^>]*))?/) do |match|
+        case
+        when match[1].nil? # e.g. /(normal)/
+          group_id = @num_groups
+        when match[2] == ':' # e.g. /(?:nocapture)/
+          @current_position += 2
+          group_id = nil
+        when %w(! =).include?(match[2]) # e.g. /(?=lookahead)/, /(?!neglookahead)/
+          # TODO: Raise exception
+        when %w(! =).include?(match[3]) # e.g. /(?<=lookbehind)/, /(?<!neglookbehind)/
+          # TODO: Raise exception
+        else # e.g. /(?<name>namedgroup)/
+          @current_position += (match[3].length + 3)
+          group_id = match[3]
+        end
+      end
       groups = parse
-      # TODO: Non-capture groups, i.e. /...(?:foo).../
-      # TODO: Named capture groups, i.e. /...(?<name>foo).../
-      MultiGroup.new(groups, this_group_num)
+      MultiGroup.new(groups, group_id)
     end
 
     def parse_multi_end_group
@@ -146,7 +160,7 @@ def parse_question_mark_repeater(group)
     end
 
     def parse_range_repeater(group)
-      match = regexp_string[@current_position..-1].match(/^\{(\d+)(,)?(\d+)?\}/)
+      match = rest_of_string.match(/\A\{(\d+)(,)?(\d+)?\}/)
       @current_position += match[0].size
       min = match[1].to_i if match[1]
       has_comma = !match[2].nil?
@@ -157,6 +171,10 @@ def parse_range_repeater(group)
     def parse_one_time_repeater(group)
       OneTimeRepeater.new(group)
     end
+
+    def rest_of_string
+      regexp_string[@current_position..-1]
+    end
   end
 end
 

spec/regexp-examples_spec.rb

@@ -52,6 +52,20 @@ def self.examples_exist_and_match(*regexps)
       )
     end
 
+    context "for complex multi groups" do
+      examples_exist_and_match(
+        /(normal)/,
+        /(?:nocapture)/,
+        /(?<name>namedgroup)/
+      )
+      # TODO: These are not yet implemented
+      # (expect to raise exception)
+#        /(?=lookahead)/,
+#        /(?!neglookahead)/,
+#        /(?<=lookbehind)/,
+#        /(?<!neglookbehind)/,
+    end
+
     context "for escaped characters" do
       examples_exist_and_match(
         /\w/,