ass="keyword">val</span> pp_diff : 
  <span><span class="optlabel">?pre</span>:<span><span>(unit, <span class="xref-unresolved">Stdlib</span>.Format.formatter, unit, unit)</span> <span class="xref-unresolved">Stdlib</span>.format4</span> <span class="arrow">&#45;&gt;</span></span>
  <span><span class="optlabel">?suf</span>:<span><span>(unit, <span class="xref-unresolved">Stdlib</span>.Format.formatter, unit, unit)</span> <span class="xref-unresolved">Stdlib</span>.format4</span> <span class="arrow">&#45;&gt