 class="fu"><a href="https://rdrr.io/r/base/cat.html" class="external-link">cat</a></span><span class="op">(</span><span class="fu">map_to_char</span><span class="op">(</span><span class="fu"><a href="https://rdrr.io/r/base/c.html" class="external-link">c</a></span><span class="op">(</span><span class="st">'a'</span> <span class="op">=</span> <span class="st">'b'</span>, <span class="st">'c'</span> <span class="op">=</span> <span class="st">'d'</span><span class="op">)</span><span class="op">)</span><span c