ince pre-processing takes place at the syntax level, before typing, type information has to be provided explicitely by mapping identifiers to type expressions.</p></div></div><div class="odoc-spec"><div class="spec value anchored" id="val-ppr_expr"><a href="#val-ppr_expr" class="anchor"></a><code><span><span class="keyword">val</span> ppr_expr : <span><a href="#type-ppr_env">ppr_env</a> <span class="arrow">&#45;&gt;</span></span> <span>?expected_type:<span><a href="#type-type_expr">type_expr</a> option</spa