How to translate base 10 number into base 2 number

Ruby
1

Hi all,

I want to write a method to tranlate base 10 number
into base 2 number. I want to call the method within
itself. But it doesn’t work. What is the right way
to do something like this?

Thanks,

Li

def ten_to_two(num1)
@array=[]
if num1>2
first,second=num1.divmod(2)
@array<<second

    #call the method itself
    ten_to_two(first)

 else
      @array<<second<<first
 end
return @array.reverse

end

puts ten_to_two(5)

##output

ruby assembly1.rb
nil
nil

2

On Mon, 15 Jan 2007, chen li wrote:

Hi all,

I want to write a method to tranlate base 10 number
into base 2 number. I want to call the method within
itself. But it doesn’t work. What is the right way
to do something like this?

This doesn’t answer your question, but in case you were not aware, Ruby
will do this conversion for you:

a = 125
puts a.to_s(2)
1111101

Kirk H.

3

Is there a way to pad the result with leading zeros
i.e. 4.to_s(2)
“100”
What I am trying to do is sort ip addresses
i.e. “192.61.14.30”
When I try to convert “192.61.14.30”
a =“192.61.14.30”.split(/./)
b = a.collect{|i| i.to_i.to_s(2) }
p b
[“11000000”,“111101”, “1110”, “11110”]
p b.join
“11000000111101111011110”.to_i

How would you pad the results of .to_s(2) to come up with a byte?

Thank you,
raymond

4

Hi Li,

First, here’s a solution:

def ten_to_two(num1)
return [] if num1 <= 0
first,second=num1.divmod(2)
ten_to_two(first) << second
end

And note that you can change the << into a call to unshift if you want
the bits in the reverse order.

As for why your solution didn’t work, let me offer two things. First,
you never do anything with the result of your recursive call to
ten_to_two. Somehow you need to combine it with the partial result you
calculated immediately beforehand. Second, you’re using instance
variables (tagged with the @). That’s generally done in methods
defined within a class to hold the state of the instance. For a
“naked” method, you generally stick to local variables (no @).

Eric

================
Interested in hands-on, on-site Ruby training? See www.LearnRuby.com
for information about a well-reviewed class.

5

On 15.01.2007 12:54, Jacob, Raymond A Jr wrote:

Is there a way to pad the result with leading zeros
i.e. 4.to_s(2)
“100”

irb(main):004:0> “%08b” % 4
=> “00000100”
irb(main):005:0> sprintf “%08b”, 4
=> “00000100”

robert

6

On 1/23/07, Roland M. [email protected] wrote:

I wonder why there isn’t support for negative radix; even though the
solutions might not be unique… who cares?

Come on, that’s like asking why fractional dimension isn’t a primitive
type in Java.

7

On Mon, 15 Jan 2007, chen li wrote:

a = 125
puts a.to_s(2)
1111101

Kirk H.

Thanks. But is is possible do the opposite, from
111101 to 125 change?

puts ‘1111101’.to_i(2)
125

Kirk H.

8

Thank you,
Raymond

9

Jacob, Raymond A Jr wrote:
(speaking of strings…)

Is there a way to pad the result with leading zeros

$ ri String#rjust

----------------------------------------------------------- String#rjust
str.rjust(integer, padstr=’ ') => new_str

  If _integer_ is greater than the length of _str_, returns a new
  +String+ of length _integer_ with _str_ right justified and padded
  with _padstr_; otherwise, returns _str_.

     "hello".rjust(4)            #=> "hello"
     "hello".rjust(20)           #=> "               hello"
     "hello".rjust(20, '1234')   #=> "123412341234123hello"

HTH

10

Kirk H.
Thanks. But is is possible do the opposite, from
111101 to 125 change?

Li

11

I wonder why there isn’t support for negative radix; even though the
solutions might not be unique… who cares?

12

On 14.01.2007 19:25, Uma G. wrote:

TAWLWTDIT

[0xFF].pack(“c”).unpack(“b8”)

there’s a whole lotta ways to do it :slight_smile:

Since we start collecting solutions…

irb(main):001:0> “%b” % 16
=> “10000”

:slight_smile:

robert

13

TAWLWTDIT

[0xFF].pack(“c”).unpack(“b8”)

there’s a whole lotta ways to do it :slight_smile:

14

— “Eric I.” [email protected] wrote:

And note that you can change the << into a call to
using instance
variables (tagged with the @). That’s generally
done in methods
defined within a class to hold the state of the
instance. For a
“naked” method, you generally stick to local
variables (no @).

Eric

Hi Eric,

Thanks for the explanations. It helps me out.

Li

15

Since we start collecting solutions…

irb(main):001:0> “%b” % 16
=> “10000”

readable and concise
beautiful !

                    UG

Uma G.

16

On 14-Jan-07, at 12:19 PM, chen li wrote:

Kirk H.

Thanks. But is is possible do the opposite, from
111101 to 125 change?

“111101”.to_i(2)
=> 125