From: Mike Stok <mike@...>
Date: 2002-10-09T02:10:30+09:00
Subject: Re: Problem with pack and Hh format specifiers

In article <1034037350.867.30.camel@awaji>, Tony Sloane wrote:
> Hi,
> 
> I'm relatively new to Ruby so perhaps I'm missing something, but I can't
> get Array's pack to work in the following situation:
> 
> irb(main):001:0> "%08b" % ["4","7"].pack ('HXh')[0]
> "00000111"
> 
> I'm expecting to see "01000111".

What are you really trying to do?

There are some ugly ways to get ['4', '7'] into a string of 1's and 0s:

irb(main):001:0> sprintf('%08b', Integer("0x" + ['4', '7'].join('')))
"01000111"
irb(main):002:0> '%08b' % [["4", "7"].join("")].pack('H*')[0]
"01000111"
irb(main):003:0> ['47'].pack('H*').unpack('B*')
["01000111"]


> Note that unpack seems to work the way I would expect.  (ASCII code for
> 'G' is 01000111.)
> 
> irb(main):002:0> "G".unpack ('HXh')
> ["4", "7"]

Depending on your context you may want to use H* as a template and split
the resulting string e.g.

irb(main):005:0> "G".unpack('H*')
["47"]
irb(main):006:0> 'banana'.unpack('H*')
["62616e616e61"]

I hope that I'm not off on some wild tangent, and that this is of some
use.

Regards,

Mike

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