SwiftManglingBNF.rb

#!/usr/bin/ruby

require 'open-uri'

MANGLING_RST_URI = "https://raw.githubusercontent.com/YOCKOW/swift/following-apple/docs/ABI/Mangling.rst"

open(MANGLING_RST_URI) {|file|
  file.each_line {|line|
    next if line !~ /^\p{Zs}*([^\p{Zs}]+\p{Zs}::=.+)$/
    modified_line = $1
    modified_line.sub!(%r{\p{Zs}*//.*$}, '')
    puts(modified_line)
  }
}