title: Using string with special characters with quo(), in rlang package
body: <p>I have two variables, a and b. I try to compute a-b using expression with the rlang package. quo(a-b) returns, as expected:</p>
  
  <pre><code>&lt;quosure: global&gt;
  ~a - b
  </code></pre>
  
  <p>However, I have a and b as strings. So I tried: quo(!!sym("a-b")), which results in </p>
  
  <pre><code>&lt;quosure: global&gt;
  ~`a-b` #(note the '')
  </code></pre>
  
  <p>So the question is why I obtain ~'a-b', and not ~a-b. How can I simply obtain ~a-b. Note that quo(!!sym("a")) returns, as expected:</p>
  
  <pre><code>&lt;quosure: global&gt;
  ~a
  </code></pre>
  
  <p>So it seems that there is an issue with the - sign (same will occur with *). Is it related to some special characters / non standard evaluation issues? How can I solve that?</p>