--- to_f

    ʸ 10 ʿɽȲᤷơư Float Ѵޤ

        p "10".to_f    # => 10.0
        p "10e2".to_f  # => 1000.0
        p "1e-2".to_f  # => 0.01
        p ".1".to_f    # => 0.1

        p "nan".to_f   # => NaN         (ruby 1.7 feature: => 0.0)
        p "INF".to_f   # => Infinity    (ruby 1.7 feature: => 0.0)
        p "-Inf".to_f  # => -Infinity   (ruby 1.7 feature: => -0.0)
        p (("10" * 1000).to_f) # => Infinity  (ruby 1.7 feature: => out of range (ArgumentError)

        p "0xa.a".to_f # => 10.625     # 16 ʤ(ƥ¸)
                                       # (ruby 1.7 feature: => 0.0)
        p " \n10".to_f # => 10.0       # Ƭζ̵뤵
        p "1_0_0".to_f # => 1.0        # `_' ϿǤȤߤʤʤ
                                       # (ruby 1.7 feature: => 100.0)
        p "".to_f      # => 0.0

    ưȤߤʤʤʤȤޤǤѴоݤȤޤ
    ѴоݤʸǤ 0.0 ֤ޤ
    
    hex, oct, to_i, 
    Integer, Float 
    ⻲ȤƤ

    դˡͤʸѴˤ 
    sprintf,
    %,
    Integer#to_s [Integer/to_s]
    Ѥޤ

