From: w wg [mailto:duzuike / gmail.com] :
#  I typed "ri Kernel", but I can't find any Kernel's class method.

C:\family\ruby>qri integer
--------------------------------------------------------- Kernel#Integer
     Integer(arg)    => integer
------------------------------------------------------------------------
     Converts _arg_ to a +Fixnum+ or +Bignum+. Numeric types are
     converted directly (with floating point numbers being truncated).
     If _arg_ is a +String+, leading radix indicators (+0+, +0b+, and
     +0x+) are honored. Others are converted using +to_int+ and +to_i+.
     This behavior is different from that of +String#to_i+.

        Integer(123.999)    #=> 123
        Integer("0x1a")     #=> 26
        Integer(Time.new)   #=> 1049896590


same w qri kernel#integer