From: "trans.  (T. Onoma)" <transami@...>
Date: 2004-10-25T01:08:20+09:00
Subject: Re: [rcr] String#first / String#last

On Sunday 24 October 2004 09:52 am, Simon Strandgaard wrote:
| New implementation is here:
|
| class String
|   def first(length=nil)
|     length ||= 1
|     unless length.respond_to?(:to_int)
|       raise TypeError, "cannot convert #{length.class} to Integer"
|     end
|     n = length.to_int
|     unless n.kind_of?(Integer)
|       raise TypeError, "#{length.class}#to_int should return Integer"
|     end
|     raise ArgumentError, "negative string size" if n < 0
|     n = [n, self.size].min
|     self[0, n]
|   end
|   def last(length=nil)
|     length ||= 1
|     unless length.respond_to?(:to_int)
|       raise TypeError, "cannot convert #{length.class} to Integer"
|     end
|     n = length.to_int
|     unless n.kind_of?(Integer)
|       raise TypeError, "#{length.class}#to_int should return Integer"
|     end
|     raise ArgumentError, "negative string size" if n < 0
|     n = [n, self.size].min
|     self[-n, n]
|   end
| end
|
|
|
|
| btw: Is this better?

Yes, I think so, but this might be even more so, 

    begin
      n = length.to_int
    rescue NoMethodError
      raise TypeError, "cannot convert #{length.class} to Integer"
    end

also

|     unless n.kind_of?(Integer)
|       raise TypeError, "#{length.class}#to_int should return Integer"
|     end

I don't think this is really needed, since such a bug would be worked out else 
where. (That #to_int might be used usefully for something other then 
returning an integer is extremely unlikely and thus not worth the check).

T.