title: How do I create pairlist with empty elements in R?
body: <p>In R, when I do </p>
  
  <pre><code>substitute(function(a) { a })[[2]]
  </code></pre>
  
  <p>I see the following pairlist:</p>
  
  <pre><code>$a
  </code></pre>
  
  <p>Note that the value of the element is empty. How can I create such a pairlist? The following doesn't work for me :</p>
  
  <pre><code>&gt; pairlist(a="")
  $a
  [1] ""
  </code></pre>
  
  <p>I am asking this in the context of programmatically creating a function. I want to do something like</p>
  
  <pre><code>&gt; call("function", pairlist(a=""), call("{", as.symbol("a")))
  function(a = "") {
      a
  }
  </code></pre>
  
  <p>This is quite close to what I get by doing</p>
  
  <pre><code>&gt; substitute(function(a){a})
  function(a) {
      a
  }
  </code></pre>
  
  <p>except for the function argument part.</p>