title: "Invalid Arithmetic Operator" when doing floating-point math in bash
body: <p>Here is my script:</p>
  
  <pre><code>d1=0.003
  d2=0.0008
  d1d2=$((d1 + d2))
  
  mean1=7
  mean2=5
  meandiff=$((mean1 - mean2))
  
  echo $meandiff
  echo $d1d2
  </code></pre>
  
  <p>But instead of getting my intended output of:</p>
  
  <pre><code>0.0038
  2
  </code></pre>
  
  <p>I am getting the error <code>Invalid Arithmetic Operator, (error token is ".003")?</code></p>