--- Float(arg)

    ư(Float)Ѵ̤֤ޤ

    ưȸʤʤʸ˻ꤷ硢㳰
    ArgumentError ȯޤ

    String#to_f [String/to_f] ⻲ȤƤ

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

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

        p Float("0xa.a") # => 10.625     # (ruby 1.7 feature: => invalid value (ArgumentError))
        p Float(" \n10") # => 10.0       # Ƭζ̵뤵
        p Float("1_0_0") # => 100.0      # `_' ǤȤߤʤ
        p Float("")      # => invalid value (ArgumentError)
        p Float(nil)     # => 0.0       # ruby 1.7 feature: cannot convert nil into Float

