title: Convert binary string to integer value using first order functions
body: <p>Given a finite list of <code>0</code> and <code>1</code>, how can I convert them to their integer value using first order function?</p>
  
  <p>The head of the list is the <strong>least significant digit</strong>. For instance, <code>1011</code> evaluates to <code>13</code>. </p>
  
  <p>In this problem, I struggle to find both the recursive step and the base step because all depends wether it's a 0 and 1. </p>
  
  <p>EDIT : </p>
  
  <p>The goal is to define a function that will compute the decimal value given a binary string. An empty list should return 0 I guess, so it would be the base case. </p>