an></span> bool</span></code></div><div class="spec-doc"><p>Check is the string is empty, i.e. consists of spaces or tabs</p></div></div><div class="odoc-spec"><div class="spec value anchored" id="val-re_spaces_upto_four"><a href="#val-re_spaces_upto_four" class="anchor"></a><code><span><span class="keyword">val</span> re_spaces_upto_four : <span class="xref-unresolved">Str</span>.regexp</span></code></div><div class="spec-doc"><p>Regular expression for sequent spaces upto four</p></div></div><div class="od