title: Scheme Lambda expression with no parentheses around parameter
body: <p>I'm having trouble understanding this example of matrix multiplication in Scheme from Rosetta Code:</p>
  
  <pre><code>(define multiplyMatrices
      (lambda (matrix1 matrix2)
          (map (lambda (row)
              (apply map (lambda column
                  (apply + (map * row column)))
              matrix2))
          matrix1)))
  </code></pre>
  
  <p>where <code>matrix1</code> and <code>matrix2</code> are each a list of lists. My question is this: Why is <code>column</code> on the fourth line not wrapped in parentheses? </p>
  
  <p>As I understand it, a <code>lambda</code> expression is of the form <code>(lambda (&lt;id1 id2 ...&gt;) &lt;exp&gt;)</code>. From testing the code I know that it works and I know that wrapping <code>column</code> in parentheses does break the program, but I don't understand how the line is even syntactical and every explanation for <code>lambda</code> expressions I find online always describes them as I did above. </p>