title: Loop "paste" function over multiple files in the same folder
body: <p>I'm trying to concatenate horizontally a number of files (1000) <code>*.txt</code> in a folder. </p>
  
  <p>How can I loop over the files using the "paste" function?</p>
  
  <p>NB: all the <code>*.txt</code> files are in the same directory. </p>