title: Standard ML: how to execute another function within a function?
body: <p>Currently, my code looks like this:</p>
  
  <pre><code>fun gradImage () =
      let val iImg = Gdimage.image(640,480) (0,0,0);
          val void = mapi gradient iImg;
      in
          Gdimage.toPng iImg "gradient.png"
      end;
  </code></pre>
  
  <p>mapi is a function with type int<em>int->int</em>int*int->image->unit. Essentially it operates on the image supplied.</p>
  
  <p>The function looks ugly with val void = ...</p>
  
  <p>How could I eliminate that?</p>