From: Tony Headford <tony@...>
Date: 2013-02-04T01:04:51+09:00
Subject: Re: Can anyone tell me the computational logic of Unpack() method of string?

What is it you don't understand exactly ?

Unpack decodes a string based on the format you specify and returns an array of the decoded elements. The format specifier is made up of a single character and may be followed by a number indicating how many times to repeat the format specifier, or a '*' to indicate all remaining elements. In the examples you provided:

1. 'A'.unpack('b*')

Will return a string representation of the binary value of 'A' in LSB first order.

2. 'A'.unpack('B*')

Will return a string representation of the binary value of 'A' in MSB first order.

3. "hello".unpack('B*')

This returns a string representation of the binary values 'h', 'e', 'l', 'l', 'o' in MSB first order 

4. "hello".unpack('C*').map { |e| e.to_s 2 }

Unpack creates an array of the integer values of 'h', 'e', 'l', 'l', 'o'. This is then iterated over to create a new array by converting each value to a string using Base2 or binary format.

Does that help ?

cheers,
Tony.


On 3 Feb 2013, at 11:58, Arup Rakshit <lists@ruby-forum.com> wrote:

>> $ 'A'.unpack('b*')
>> => ["10000010"]
>> 
>> $ 'A'.unpack('B*')
>> => ["01000001"]
>> 
>> $ "hello".unpack('B*')
>> => ["0110100001100101011011000110110001101111"]
>> 
>> $ "hello".unpack('C*').map {|e| e.to_s 2}
>> => ["1101000", "1100101", "1101100", "1101100", "1101111"]
>> 
> 
>> But couldn't understand the logic. So any help would be appreciated!
>> Thanks,
> 
> Can anyone help me here to understand?
> 
> -- 
> Posted via http://www.ruby-forum.com/.
>