From: Brian Candler <b.candler@...>
Date: 2009-02-16T05:52:45+09:00
Subject: Re: Ruby-newbie

Terje Haarstad wrote:
>> sum = buff[0] + buff[1] + buff[2] + buff[3]
>> svar = [sum & 0xffffffff].pack("I")
> 
> Why do u have to use sum & 0xffffffff? an error occour
> (`pack': bignum too big to convert into `unsigned long' (RangeError)
> from vortex0.rb:16) if i DONT use 0xfffffffff while use s.gets
> but why do they conflict with each other?

Ruby numbers don't wrap around - they can grow indefinitely large.

Sometimes the four random 32-bit numbers add up to a 33-bit number. In 
this case, the server is expecting you to truncate the result to 32 
bits. If you don't truncate explicitly, Array#pack will abort because 
the number you're asking it to fit into a 32-bit space is too big.

HTH,

Brian.
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