Variablen, Zahlen und Strings

name = "Mia"                 # lokale Variable
alter = 17
PI = 3.14159                 # Konstante (Großbuchstaben)
$global = "selten sinnvoll"  # globale Variable
@instanz = "in Objekten"     # Instanzvariable

a, b = 1, 2
a, b = b, a                   # tauschen
erst, *rest = [1, 2, 3, 4]
puts "#{a} #{b} #{erst} #{rest}"
x = y = 5
puts x + y
puts defined?(name)
puts defined?(nirgendwo).inspect

puts 7 + 2, 7 - 2, 7 * 2, 7 / 2, 7 % 3, 2 ** 10     # Ganzzahldivision!
puts 7 / 2.0
puts 7.fdiv(2)
puts 7.divmod(2).inspect
puts 10.0 / 3
puts (10.0 / 3).round(2)
puts 3.7.floor, 3.2.ceil, 3.5.round, -3.5.round, 3.14159.truncate
puts 2**100                      # beliebig große Ganzzahlen
puts 1_000_000
puts 0b1010, 0o17, 0xff
puts 255.to_s(2), "ff".to_i(16)
puts 10.gcd(4), 10.lcm(4)
puts Integer.sqrt(50), Math.sqrt(144), Math::PI.round(3)
puts 0.1 + 0.2
puts (0.1 + 0.2 - 0.3).abs < Float::EPSILON
puts 5.clamp(1, 3), 1234.digits.inspect
puts rand(1..1).to_s + " (Zufall mit festem Bereich)"

s = "Hallo Welt"
puts s.length, s.upcase, s.downcase, s.capitalize, s.swapcase
puts s[0], s[-1], s[0, 5], s[0..4], s[6..]
puts s.sub("Welt", "Ruby"), s.gsub("l", "L")
puts s.include?("Welt"), s.start_with?("Hal"), s.end_with?("x")
puts s.index("W"), s.count("l")
puts s.split.inspect, "a,b,c".split(",").inspect
puts s.reverse, s.chars.first(3).inspect
puts "  trim  ".strip + "|", "x".center(5, "*"), "7".rjust(3, "0"), "ab".ljust(4, ".") + "|"
puts "ab" * 3, "a" + "b", "a" << "b"
puts "Ruby" <=> "Rubx", "a" == "a", "a".equal?("a")
puts "%05.1f | %-5s| %+d | %x" % [3.14159, "ab", 5, 255]
puts "Zahl: #{'%.2f' % 3.14159}"
puts "ä".bytes.length, "ä".length
puts "ruby ist schön".split.map(&:capitalize).join(" ")
puts "text".frozen?
puts 'Einfache Quotes: #{kein} \n bleibt'
puts "Tab:\tZeilenumbruch folgt\nnächste Zeile"

text = <<~HEREDOC
  Mehrzeilig
    mit Einrückung
  und #{1 + 1} Interpolation
HEREDOC
puts text

puts :ruby.class
puts :ruby.object_id == :ruby.object_id
puts "ruby".object_id == "ruby".object_id
puts :ruby.to_s, "ruby".to_sym.inspect
puts %i[a b c].inspect, %w[x y z].inspect

[nil, false, 0, "", [], "false"].each { |w| puts "#{w.inspect} => #{w ? 'wahr' : 'falsch'}" }
puts nil.to_a.inspect, nil.to_s.empty?, nil.inspect
x = nil
puts x&.length.inspect         # sicherer Aufruf: nil statt Fehler
puts (x || "Standard")
x ||= "gesetzt"
puts x

puts "42".to_i + 1, "3.7".to_f, 42.to_s + "!", "abc".to_i, "12abc".to_i
puts Integer("42"), Float("3.5")
begin
  Integer("abc")
rescue ArgumentError => e
  puts "Fehler: #{e.message}"
end
puts Integer("abc", exception: false).inspect
puts 65.chr, "A".ord, 3.7.to_i, 5.to_f, [1, 2].to_s, nil.to_a.inspect
puts Array(nil).inspect, Array(1..3).inspect, String(5)