versing SIL data types</a></li><li><a href="#substitution">Substitution</a></li><li><a href="#functions-for-replacing-occurrences-of-expressions.">Functions for replacing occurrences of expressions.</a></li><li><a href="#functions-for-constructing-or-destructing-entities-in-this-module">Functions for constructing or destructing entities in this module</a></li></ul></nav><div class="odoc-content"><div class="odoc-spec"><div class="spec module" id="module-F" class="anchored"><a href="#module-F" class="anchor"