Ruby Iteration Question : Binary->Decimal Program

Question

I am learning Ruby and thought of making a Binary->Decimal converter. It gets a binary string and converts to decimal equivalent. Is there a way to keep track of the current iteration step in ruby so that the variable 'x' can be removed?

def convert(binary_string)
    decimal_equivalent = 0
    x=0   
    binary_string.reverse.each_char do |binary|
    decimal_equivalent += binary.to_i * (2 ** x)
    x+=1
    end

   return decimal_equivalent
end

Answer 1

binary_string.reverse.chars.each_with_index do |binary, i|
  decimal_equivalent += binary.to_i * (2 ** i)
end

Or on versions older than 1.8.7:

binary_string.reverse.split(//).each_with_index do |binary, i|
  decimal_equivalent += binary.to_i * (2 ** i)
end

Answer 2

Yes, by using the very powerful enumerator library:

require 'enumerator'
def convert(binary_string)
  decimal_equivalent = 0
  binary_string.reverse.enum_for(:each_char).each_with_index do |binary, i|
    decimal_equivalent += binary.to_i * (2 ** i)
  end
  return decimal_equivalent
end

Incidentally, you may be interested in Array#pack, and String#unpack. They have support for bit strings. Also, an even easier way to get this result is to use #to_i, e.g. "101".to_i(2) #=> 5